Milltek Sport Exhaust Systems

What is the best Milltek exhaust for a WRX? Milltek's cat-back systems for the 15-21 WRX and WRX STI — offered with Cerakote Black, GT100, and GT-115 tip finishes in resonated and non-resonated configurations — are the flagship picks, pairing a refined European tone with daily-drivable volume. The line also covers the 2020+ Toyota GR Supra and the FR-S, BRZ, and 86 chassis, so check your year and model for the right system.

A cat-back replaces everything behind the catalytic converters: the mid-pipe, muffler, and tips. Milltek's approach is modular — choose resonated for a quieter, drone-free cruise or non-resonated for a louder, more aggressive note, then pick your tip finish. The GT-115 burnt titanium and polished tips on the Supra systems and the Cerakote Black tips on the WRX systems let you match the exhaust to the car's look as much as its sound. If a turbo-back or downpipe upgrade is also on your list, see our cat-back collection for the full picture.

Milltek is a UK-based performance exhaust manufacturer whose systems for the 15-21 WRX and WRX STI include Cerakote Black tip and 3-inch GT100 tip variants, plus front-pipe-back systems for the 2020+ GR Supra in non-resonated, non-valved "louder" configurations with GT-115 burnt titanium, Cerakote Black, or polished tips, and a secondary cat-back with titanium tips for the FR-S, BRZ, and 86. Grimmspeed is the Subaru-focused counterpart in our catalog, building downpipes, j-pipes, and cat-backs engineered specifically around WRX and STI fitment. Cobb Tuning pairs its Accessport tuning ecosystem with exhaust systems designed to work with its staged packages. Magnaflow rounds out the exhaust aisle with its own long-running line of performance cat-back systems across many platforms.

Standouts in this collection include the Milltek 3-inch cat-back with Cerakote Black tips for the 15-21 WRX STI and the Supra front-pipe-back with GT-115 burnt titanium tips. Supra owners can also browse our GR Supra parts collection, and everyone shopping exhaust should read our guide to the best exhaust for the Subaru WRX.

Is a Milltek cat-back louder than stock?

Yes — Milltek offers resonated systems for a refined, drone-free tone and non-resonated systems for a louder, more aggressive note. Pick resonated if the car is a daily driver and non-resonated if you want maximum presence.

Does a cat-back require a tune?

A cat-back alone does not require a tune on most cars, since it sits behind the catalytic converters and factory sensors. It is a safe first exhaust upgrade; downpipe or turbo upgrades are where tuning becomes necessary.

What is the difference between the GT-115 tip finishes?

GT-115 refers to the tip size and style; finishes like burnt titanium, Cerakote Black, and polished are cosmetic choices that do not change sound or performance — pick the one that matches your build.

Will the Milltek WRX system fit my STI?

Fitment is year- and model-specific — the 15-21 WRX and WRX STI systems in this collection are listed separately, so confirm your exact year and model in the product title before ordering.