Audi S3 8V Cat-Back Exhaust: MBRP vs AWE (2015-2018)

If you own an 8V chassis Audi S3, you already know the car is faster than it sounds. Audi voiced the factory EA888 like a polite executive sedan — quiet, polished, and honestly a little embarrassing when you roll onto boost and hear almost nothing happen. The right Audi S3 8V cat-back exhaust (2015-2018) fixes that in an afternoon. At NLP Performance in Tampa, we’ve shipped all three of the systems in this guide to S3 owners from Hyde Park to Wesley Chapel, and today we’re putting them head-to-head: the budget hero from MBRP, AWE’s unapologetic Track Edition, and the dual-mode AWE SwitchPath for drivers who want both lives.

The 8V S3 Stock Exhaust: Why Owners Replace It

Audi’s factory engineers gave the 8V S3 what we half-jokingly call “whispering torque” tuning. The stock system runs roughly 2.57-inch piping pre-resonator and about 2.78-inch post-resonator, weighs in around 46 pounds, and leans on a valve-actuated quad-tip muffler that stays mostly shut unless you’re in Dynamic mode with the throttle buried. It’s heavy, restrictive, and voiced to offend absolutely nobody — which, if you bought an S3, is probably not what you signed up for.

The EA888 Gen 3 is a turbocharged 2.0L that genuinely wants to breathe. On a stock tune you’ll feel a small seat-of-the-pants improvement from a cat-back. Once you add a tune and especially a 3-inch downpipe, the cat-back is what lets the whole package finally exhale. Community dyno data consistently shows 5–10 whp on tuned cars with a proper cat-back, and AWE publishes +7 whp / +2 wtq stock cat-back only, climbing to +12 whp / +9 wtq on turbo-back configurations.

What to Look for in an S3 Cat-Back

Before we jump into the three systems, here’s the short list we walk every customer through on the phone:

• Material. T304 or T304L stainless is the floor. Anything less is going to rust out faster than your tune can pay for itself.
• Diameter. A true 3-inch cat-back is the right call if you’re running or planning a 3-inch downpipe. All three systems here step down to 2.5-inch at the back half to balance flow and tone.
• Valve behavior. The factory S3 exhaust flap is driven by the ECU through Drive Select. Some aftermarket systems delete the valve entirely (MBRP, AWE Track). The AWE SwitchPath keeps factory valve actuation and bolts on a remote for manual control.
• Stock vs 3-inch downpipe. All three of these cat-backs accept the stock downpipe Y-pipe flange and also mate to aftermarket 3-inch downpipes. You do not need to install a downpipe first to run them.
• Drone. Every non-valved 3-inch system on this chassis will drone to some degree at highway cruise. The amount varies wildly. We’ll be honest about it below.

MBRP S4601304: The Budget Bolt-On That Punches Above $1K

This is the one we recommend most often, and it’s the reason we wrote this article. The MBRP 15-18 Audi S3 304SS 3" Quad Split Rear Exit system gives you nearly everything the boutique brands offer at roughly two-thirds the price of AWE Track and less than half the price of SwitchPath.

On the road, the MBRP has what we’d call the most broadly usable tone of the three. Cold starts are civilized enough that your neighbors won’t file HOA complaints. Lay into the throttle and it opens up into a proper turbo-four growl — hints of that rally-car rasp the EA888 is famous for once you let it breathe. Highway cruise at 75 mph on I-275 is remarkably calm; the low drone is noticeably present around 2,000–2,200 rpm but never crosses into “I can’t take a phone call” territory. Remember that this system deletes the factory valve, so there’s no dynamic quiet mode — what you hear is what you get, all the time.

AWE Track Edition: When You Want It Loud, Full Stop

AWE’s Track Edition is the answer for owners who’ve decided the S3 should sound like a WRC car pulled off the stage and driven to work. It’s handcrafted T304L stainless, US-sourced tubing, 3-inch into 2.5-inch, with no driver-side muffler and no valve. There is nothing polite about it.

Let’s be direct, because our customers deserve it: the AWE Track Edition drones. Forum consensus and our own customer feedback consistently report pronounced cabin drone at 2,000–2,500 rpm cruise — exactly the rpm band where a 6-speed manual or dual-clutch S3 lives on the highway. If your daily involves thirty minutes of I-275 between Tampa and Brandon, you will feel this exhaust in your chest cavity. That is the price of admission for the sound it makes when you’re on it. And when you are on it, it is spectacular: hard-edged, mechanical, and a little bit terrifying in the best way. AWE publishes gains of +7 whp / +2 wtq cat-back only and +12 whp / +9 wtq turbo-back, plus their No CEL Guarantee, which is a meaningful piece of reassurance on a car whose ECU is notoriously chatty.

AWE SwitchPath: The Commuter’s Track Car

The SwitchPath is AWE’s answer to the drone complaint, and honestly it’s the exhaust we wish every S3 owner could afford. Same T304L stainless, same 3-inch / 2.5-inch geometry, same 102mm tip options as the Track Edition — but with a factory-style valve that flips between a civilized “Touring” path and a Track-style open path on demand. It reads the factory valve signal, so Audi Drive Select does the work: Auto and Comfort keep the valve closed, Dynamic opens it. Add the optional AWE SwitchPath Remote and you get manual override from the driver’s seat.

The SwitchPath is a genuine dual-personality system. In closed mode, drone is minimal — you’re closer to stock-plus than aftermarket. Open it up and it’s within earshot of the Track Edition: big, angry, and turbo-four mean. Our customers who commute from Tampa up to Wesley Chapel or out to Lakeland tell us the valve alone justifies the premium over Track. You get the Track Edition experience when you want it and a highway cruise that doesn’t require noise-canceling headphones.

Head-to-Head: Sound, Drone, Weight, and Gains

*MBRP gains based on community dyno reports on tuned cars; not manufacturer-published.

Installation & Tune Pairing

All three of these systems are bolt-on to the factory 3-inch downpipe Y-pipe flange. Plan on 2–4 hours for a DIY install on jack stands or a lift, with basic hand tools and a penetrating oil for the factory hangers. The hangers fight you more than the bolts do — we’ve seen one or two 8V S3 cars where the rear hanger rubber was fused enough that we recommended fresh hangers as a courtesy add-on.

On tune pairing: a cat-back alone on a stock tune is primarily a sound and weight mod. The real power story shows up when you stack a Stage 1 tune and a 3-inch downpipe. That’s when the EA888 starts seeing the airflow the exhaust was designed around, and that’s where AWE’s +12 whp / +9 wtq turbo-back number comes from. If you’re planning to stay stock, any of these three will still transform the car’s character — just don’t expect a dyno miracle without a tune.

Which S3 Exhaust Should You Buy?

The daily driver who wants the EA888 to have a voice: Buy the MBRP S4601304. It’s the most forgiving on long commutes, sounds great when you’re on throttle, and leaves money in the budget for a tune and a downpipe.

The weekend enthusiast who doesn’t commute far: Buy the AWE Track Edition. If your S3 is a second car, a canyon weapon, or a track day toy, the drone stops mattering and the sound becomes the reason you drive.

The dual-purpose commuter-to-canyon driver: Buy the AWE SwitchPath. It’s genuinely two exhausts in one, and it’s the only system on this list that lets you hand the keys to your spouse without an apology.