Next Level Performance
September 6, 2026 • 11 min read
The 2024+ Ford Mustang GT and Dark Horse (S650) arrive with a strong 5.0L Coyote V8 — 480 horsepower in the GT and 500 in the Dark Horse — but the factory cast exhaust manifolds are the single biggest airflow restriction on the engine. Swapping them for a set of Kooks long-tube headers is the classic way to wake up a naturally aspirated Coyote, and Kooks’ 2024 Mustang GT / Dark Horse 304 stainless kit (part 1151H642) is the most complete bolt-on solution NLP Performance stocks for the S650. This review breaks down the construction, the real-world power story, emissions legality, and the best cat-back exhausts to pair with them.
Our Verdict
The Kooks 304 stainless long-tube headers are the best breathing upgrade for a naturally aspirated 2024+ S650 Coyote.
With 2in mandrel-bent primaries, 3in collectors, and EPA-verified 300-cell GREEN high-flow cats good for 750+ RWHP, this kit adds meaningful mid-range and top-end power on the GT and Dark Horse while staying street-friendly. Pair it with a valved cat-back and a supporting tune for the full effect.
Shop Our Top Pick →What Makes the Kooks Long-Tube Headers a Standout for the S650?
The Kooks kit is a full-length long-tube header design built from 304 stainless steel and handcrafted in the USA, where Kooks has been building race-proven exhaust since 1962. Unlike the restrictive cast-iron manifolds Ford bolts on at the factory, long-tube headers use equal-length mandrel-bent primary tubes that scavenge exhaust gas far more efficiently, which is where the power gains come from on a Coyote.
The engineering details are what separate Kooks from budget headers. Each header uses 2-inch mandrel-bent primaries feeding into 3-inch collectors with Kooks’ patented Scavenging Spike, mounted to 3/8-inch thick laser-cut flanges with a dual bolt pattern for a leak-free seal. The kit ships with High Output GREEN catted connection pipes, OEM adapters, gaskets, an oxygen-sensor extension harness, clamps, and a complete bolt kit — Kooks states no additional parts are required for the install.
Kooks 304 stainless long-tube headers with 2in mandrel-bent primaries.
Key Specifications
How Much Power Do Long-Tube Headers Add to a 2024+ Mustang GT?
Long-tube headers commonly add roughly 15 to 30 rear-wheel horsepower and a similar torque figure on a naturally aspirated 5.0L Coyote once the car is retuned, with the largest gains in the mid-to-upper RPM range where the factory manifolds choke flow the hardest. On the S650 platform — the 2024 Mustang GT makes 480 hp and 415 lb-ft (486 hp with the active exhaust), and the Dark Horse makes 500 hp and 418 lb-ft — headers are the highest-impact naturally aspirated bolt-on you can install.
The key word is tuned. Headers change exhaust scavenging and shift the air-fuel data the factory ECU reads, so a custom or off-the-shelf tune is what actually converts the improved flow into usable power and keeps drivability sharp. Installed and tuned, the Kooks headers also transform the exhaust note, adding the deep, race-bred rasp long-tubes are known for. For forced-induction builds down the road, the 300-cell GREEN cats are engineered to support more than 750 rear-wheel horsepower, so the kit will not become the bottleneck if you add a supercharger later.
3in Kooks collectors use a patented Scavenging Spike for stronger exhaust extraction.
Kooks 2024 Mustang GT / Dark Horse Long-Tube Headers
What We Like
- + 304 stainless, USA-made with 2in primaries and 3in collectors for maximum Coyote scavenging
- + EPA-verified 300-cell GREEN high-flow cats keep it street-friendly and support 750+ RWHP
- + Complete kit — gaskets, O2 extensions, clamps and bolts included, no extra parts needed
- + Fits both the 480-hp GT and 500-hp Dark Horse (and 2015–2023 S550 GT)
Things to Consider
- – Premium price point reflects the full catted long-tube design
- – A supporting tune is required to realize the full power gain
- – Long-tube installation is labor-intensive and best left to an experienced shop
Are the Kooks GREEN Catted Connection Pipes Street-Legal?
The Kooks S650 kit is designed to stay street-friendly. Its High Output GREEN connection pipes carry EPA-verified 300-cell high-flow catalytic converters, so the system keeps functioning cats in place and helps avoid the check-engine light and emissions failures that come with catless or off-road pipes. That makes these headers a smart pick for a daily-driven Mustang that still needs to pass an emissions check in most states.
Two caveats. First, CARB states such as California enforce stricter aftermarket exhaust rules, so verify your local emissions requirements before ordering. Second, if you plan to keep the factory cat-back exhaust and just want a mid-pipe upgrade, the Borla SwitchFire X-Pipe is an off-road (non-CARB) OE-resonator replacement — a different, less expensive path than a full long-tube swap.
Kooks High Output GREEN 300-cell high-flow catted connection pipes.
Best Cat-Back Exhausts to Pair With Your Kooks Headers
Headers handle the front half of the exhaust; a cat-back completes the system from the connection pipes to the tips and sets the sound. All three of the S650-specific systems below are valved active-exhaust designs in 304 stainless, so they retain the factory quiet-start and drive-mode functionality. The table compares the three most popular pairings NLP Performance stocks for the 2024+ Mustang GT and Dark Horse.
| Kit | Valve Type | Tips | Sound Profile | Price |
|---|---|---|---|---|
| AWE SwitchPath Cat-BackTop Pick | Dual-mode valved | Quad Diamond Black | Switchable: quiet to roar | $3,195.00 |
| Borla ATAK Cat-Back | Active-valve | Quad Carbon Fiber | Loudest, most aggressive | $3,264.99 |
| Corsa 3in Dual Rear Cat-Back | Valved w/ RSC | Twin 4.5in Black PVD | Aggressive, drone-free cruise | $2,429.99 |
AWE SwitchPath Cat-Back — Best All-Around Pairing
The AWE SwitchPath is the most versatile match for the Kooks headers. Its valved design lets you toggle between a near-stock quiet mode for the neighborhood and a full-volume roar at the push of a button, while retaining the S650’s factory active-exhaust behavior. The quad diamond-black tips and precision 304 stainless build make it the pairing we recommend for most owners.
Borla ATAK Cat-Back — Loudest and Most Aggressive
If you want the most aggressive tone available, the Borla ATAK is the answer. ATAK is Borla’s highest-volume acoustic profile, and this S650 system runs a 3-inch true-dual layout with a merge X-pipe, active-valve control, Borla’s Polyphonic Harmonizer technology, and carbon-fiber tips. It is the pick for owners who want the Dark Horse to announce itself.
Corsa 3in Dual Rear Cat-Back — Drone-Free Daily Driver
Corsa builds its S650 system around a 3-inch dual-rear-exit layout, a Double Helixx X-pipe, and the brand’s Reflective Sound Cancellation (RSC) technology, which is engineered to deliver an aggressive tone at wide-open throttle while eliminating the interior drone that fatigues you on the highway. Twin 4.5-inch black PVD tips finish the look. At $2,429.99 it is also the value pick of the three.
Keeping the Factory Cat-Back? Add the Borla SwitchFire X-Pipe
Not ready for a full cat-back? The Borla SwitchFire X-Pipe is an OE-resonator replacement that drops in ahead of the factory cat-back to sharpen throttle response and free up the mid-pipe. It is an off-road (non-CARB) part, so it is intended for track use where emissions rules allow, and at $669.99 it is the budget route to a meatier note behind your Kooks headers.
Installation: What to Know Before Installing S650 Headers
Long-tube header installation is one of the more involved bolt-ons on a modern Mustang. Because the primaries route around the steering shaft and the K-member, the job typically requires raising the engine or dropping the subframe on the S650, and plan on 6 to 10 hours of labor. Kooks includes the gaskets, O2 sensor extension harness, clamps, and bolt kit needed, so there are no surprise parts, but this is not a driveway job for most owners.
Our recommendation from the NLP Performance shop in Tampa, FL: budget for a professional installation and a dyno or handheld tune in the same visit. Doing the header install and the supporting tune together means the car comes off the lift running right, with the fault codes cleared and the air-fuel dialed in. If you are shipping the kit out of state, our team can confirm fitment for your exact trim and help you match the right cat-back and tune before you order.
A valved cat-back like the AWE SwitchPath completes the Kooks header system.
Frequently Asked Questions
How much horsepower do long-tube headers add to a 2024 Mustang GT?
Long-tube headers typically add about 15 to 30 rear-wheel horsepower and a similar torque figure to a naturally aspirated 5.0L Coyote once the car is retuned, with the biggest gains arriving in the mid-to-upper RPM band. On a 2024 Mustang GT (480 hp / 415 lb-ft) or 500-hp Dark Horse, the Kooks 2in primaries and 3in collectors free up exhaust flow the restrictive factory cast manifolds choke off. A supporting tune is required to realize the full gain.
Are Kooks GREEN catted headers street-legal?
Yes. The Kooks S650 kit uses High Output GREEN connection pipes fitted with EPA-verified 300-cell high-flow catalytic converters, so it retains functioning cats and keeps a check-engine light away on most street cars. That is different from an off-road or catless connection pipe. California and other CARB states have stricter rules, so always confirm your local emissions requirements before buying.
What is included with the Kooks 2024 Mustang header kit?
The Kooks 1151H642 kit includes the pair of 304 stainless long-tube headers, the High Output GREEN catted connection pipes, OEM adapters, gaskets, an oxygen-sensor extension harness, clamps, and the bolt kit. Kooks states no additional parts are required for installation, so it bolts up to the factory cat-back or an aftermarket cat-back exhaust.
Do I need a tune after installing headers on my S650 Mustang?
A tune is strongly recommended. Long-tube headers change exhaust scavenging and the air-fuel readings the factory ECU sees, so a custom or off-the-shelf tune is needed to optimize timing and fueling, recover drivability, and unlock the full power gain. Running headers without a tune can leave power on the table and trigger fault codes.
What size are the Kooks Mustang header primaries and collectors?
The Kooks S650 headers use 2-inch mandrel-bent primary tubes feeding into 3-inch collectors with Kooks' patented Scavenging Spike, mounted to 3/8-inch thick laser-cut flanges with a dual bolt pattern. The GREEN cats are 300-cell high-flow units engineered to support builds making more than 750 rear-wheel horsepower.
Which cat-back exhaust should I pair with Kooks headers?
For most 2024+ Mustang GT and Dark Horse owners, the AWE SwitchPath is the best all-around pairing because its valves let you switch between a quiet commute and a full-volume roar while keeping the factory active-exhaust functionality. The Borla ATAK is the pick if you want the loudest, most aggressive tone, and the Corsa system uses RSC technology to minimize in-cabin drone at cruise.
Does NLP Performance ship the Kooks Mustang headers for free?
The Kooks 2024 Mustang GT and Dark Horse header kit is in stock at NLP Performance and is currently listed with an Extra 5% off promotion, priced at $3,817.64 (MSRP $4,241.82). Our Tampa, FL team can confirm current shipping options, tune pairings, and fitment for your exact trim before you order.
Ready to Wake Up Your S650 Coyote?
Shop the Kooks 2024+ Mustang GT and Dark Horse headers plus the cat-backs to complete your build at NLP Performance.
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