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2011 Subaru STI - Milltek Sport Turboback Exhaust & Takeda Air Intake - Proving Grounds

Giving the ’11 Subaru STI some serious breathing capacity.

Test Mule

’11 Subaru STI

2.5-liter EJ25 turbocharged 4-cylinder
Relevant Mods

The latest iteration of Subaru’s STI is back on track with its aggressive widebody stance and the fabled rear wing that was lost for a generation. There’s no doubting that the looks of the STI are on par with the best out there, but the new STI has lost a bit of its older sibling’s edge when it comes to performance. Its sluggish, lackluster power output needs a serious overhaul to deliver the type of performance we expect from a car of this nature.

The problem is with emissions and Subaru’s aging EJ25 engine having to meet strict requirements to pass them. The solution is simple, though — with a few mods and a proper tune, the beast within the STI is awakened.

First and foremost, the restrictive exhaust needs to be replaced with a quality-built, high-flow unit such as Milltek’s Sport turboback exhaust system from its exclusive North American Subaru dealer, Mann Engineering. Built and designed at home in England, the system is made from 100 percent 304 stainless steel and features a high-flow design utilizing a 3-inch bellmouth downpipe and a HJC Motorsports 100-cell count high-flow catalytic converter that’s built to withstand high heat and the abuse of a turbocharger. The rest of the system flows out to dual 2.325-inch mufflers that can be equipped with either 100mm titanium or polished stainless steel exhaust tips for a sleek OEM-like look.

On the intake side, the STI can also use a helping hand, and Takeda’s air intake is built to replace the front portion of the OEM intake setup. The anodized polished pipe places the dry filter element that’s surrounded by a heat shield into the STI’s front fenderwell, providing constant access to fresh air. Flow is said to increase 63 percent over its stock counterpart — a serious power boost.

Results: Milltek Exhaust
Plain and simple, the STI is a dog right off the showroom floor. It tries hard to deliver some type of excitement, but you can feel the ECU fighting the engine to ensure that any power it makes is done so in a clean, environmentally friendly way.

Time to change all that (and still be environmentally conscious). The Milltek exhaust that was installed on our test mule proved to be the ideal upgrade for this ’11 STI sedan. With such an intricate turboback exhaust, fitment issues can arise, but the Milltek is broken down into many small sections to ensure OEM-like tolerances and clearances. The factory O2 sensor is about the only thing that has to be moved from its original spot and placed further down the exhaust path, which requires some unclipping of plastic ties, but otherwise the system installs in just over an hour. The quad exhaust tips that are clamped onto the mufflers are adjustable, so you can set them to your desired length. If you have some extra cash, then we recommend splurging on the titanium tips because they add a unique look that you won’t find on other systems.

Sound-wise, the Milltek exhaust is an ideal blend of low rumble and aggressive, wide-open-throttle notes. Never does it annoy or drone during cruising — at times, you forget it’s even there (and we’re sure the police will, too).

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