Evo X Downpipe: AMS vs Invidia vs Cobb (2008-2015)

Ask any tuner and they will tell you the same thing: the best first mod for a 2008–2015 Mitsubishi Evo X is a downpipe. The 4B11T’s factory downpipe wears a restrictive catalytic converter that chokes the TD05H turbo right where it matters. Swap in a free-flowing 3-inch Evo X downpipe and you unlock quicker spool, a fatter mid-range, and the headroom every higher-boost tune needs. In this comparison we put the three downpipes we stock at NLP Performance head to head — the AMS Widemouth, the Invidia one-piece high-flow catted, and the Cobb 3in 304 stainless — so you can pick the right one for your GSR, MR, or Ralliart.

Why the downpipe is the Evo X’s best first bolt-on

A downpipe is the best first bolt-on for the Evo X because it removes the biggest airflow restriction between the turbo and the exhaust. The 4B11T 2.0L turbo four makes 291 hp and 300 lb-ft at the crank from the factory — roughly 264 whp and 292 lb-ft on a stock GSR — while the TD05H-152G6-12T turbo is capable of 350–400 whp on the stock block. The factory downpipe and its dense catalytic converter are the choke point. Opening that up lets exhaust gas leave the turbine faster, so the turbo spools sooner and the car pulls harder out of every corner.

On the 4B11T, the downpipe’s biggest measurable gains show up as torque and spool rather than a huge peak-horsepower jump. Independent dyno testing of a bolt-on downpipe with a matched re-tune has shown gains of nearly 30 lb-ft under the curve with the same boost. More importantly, the downpipe is the enabler: paired with a Cobb Accessport flash and a cat-back exhaust, many stock-turbo Evo X owners see 300–320+ whp. Skip the downpipe and you leave that ceiling on the table.

The 3 best Evo X downpipes compared

Each of these downpipes targets a different Evo X owner. The AMS Widemouth is built for maximum flow and big-power builds, the Cobb is the value pick that plugs straight into the Accessport ecosystem, and the Invidia is the street-minded choice with a high-flow catalytic converter still in the pipe. Here is how each one stacks up.

1. AMS Performance Widemouth Downpipe — Best for power

AMS calls this “the most power-producing and well-designed downpipe on the market” for the Evo X, and the design backs it up. The “Widemouth” opening unshrouds the turbine outlet of the factory TD05H turbo, and the kit includes a matched turbo outlet pipe so the whole path from turbine to mid-pipe flows freely. It is a catless race pipe, which is why it is the go-to on high-boost and upgraded-turbo builds where every bit of flow counts. At around $580 it sits in the middle of this group on price, but it is the one to buy if your Evo X is heading past 400 whp.

2. Invidia One-Piece Downpipe + High-Flow Cat — Best for the street

Invidia’s one-piece downpipe is the street-friendly pick because it keeps a high-flow catalytic converter in the pipe. That cat cuts the rasp and rotten-egg smell that catless pipes are known for and helps keep a check-engine light at bay on a mild tune, while still flowing far better than the restrictive OEM cat. The one-piece construction also simplifies the install versus a two-piece design. Note that Invidia lists this part as not available for shipment to California due to CARB regulations, so it is intended for use where a high-flow cat is permitted. It carries the highest price of the three here, though it is currently marked well below its list price.

3. Cobb 3in 304 SS Downpipe — Best value

The Cobb 3-inch 304 stainless downpipe is the value champion at around $300, and it is the natural choice if you are already in the Cobb ecosystem. Cobb designs its off-the-shelf (OTS) Accessport maps around this downpipe, so pairing the two means your tune already accounts for the extra flow — no guesswork. It is a catless pipe, so it is loud and off-road-use only, but it is also the easiest, cheapest way to take a stock-turbo Evo X to a proper Stage 2 setup. It even covers the 2009–2015 Ralliart, which shares much of the drivetrain.

Evo X downpipe comparison table

Here are the three Evo X downpipes side by side. The right choice comes down to whether you want maximum flow, a street-legal-style cat, or the best price on a tune-matched pipe.

Catted vs catless: which Evo X downpipe is right for you?

Choose a catted downpipe if your Evo X is street-driven and you want it quieter and less smelly; choose catless if the car is track-focused and you want maximum flow. The Invidia is the only catted option in this test — its high-flow converter tames drone and helps a mild tune pass without a check-engine light, at a small cost in top-end flow. The AMS Widemouth and Cobb are both catless race pipes: they flow the most and cost less to build, but they are loud, will typically trigger a CEL without a tune that addresses the rear O2 sensor, and are labeled for off-road or competition use only.

A practical rule of thumb: a daily-driven Evo X that still needs to behave in traffic is happiest with the Invidia catted pipe, while a dedicated build chasing 350–400+ whp on the stock block is better served by the AMS Widemouth or the budget Cobb. Whichever you pick, plan on a tune to realize the gains and clear codes.

How much power does an Evo X downpipe add?

An Evo X downpipe adds the most gain in torque and turbo response rather than peak horsepower, and it needs a supporting tune to be worth it. On the stock TD05H turbo, a downpipe with a matched re-tune has shown gains of roughly 20–30 lb-ft under the curve at the same boost, with the turbo lighting up noticeably earlier. As a package — downpipe, an intake, a cat-back exhaust, and a Cobb Accessport flash — a stock-turbo GSR or MR commonly lands in the 300–320+ whp range, versus roughly 264 whp stock. The downpipe is the piece that makes the rest of that possible by removing the exhaust restriction the factory cat creates.

Installation and tuning notes

Installing an Evo X downpipe is a bolt-on job for a competent DIYer, but budget a few hours and fresh hardware. Plan on new turbo-to-downpipe and downpipe-to-cat-back gaskets, penetrating oil for the factory nuts, and access from below on a lift or jack stands. On the SST (MR) and 5-speed (GSR) cars the downpipe itself is the same — the transmission does not change the fitment. The most important step is the tune: flash a Stage 2 map with your Cobb Accessport (or an EcuTek/other calibration) so fueling and the O2 strategy match the new pipe. That is what unlocks the gains, keeps air-fuel safe, and prevents the check-engine light that a catless pipe would otherwise set. At NLP Performance we always recommend pairing any Evo X downpipe with a proper tune before you lean on the boost.