The Process West range billet manifolds is a no holds barred manifestation of what is possible under the hood of a WRX/STI when perfect aesthetics meet high end performance. What you see here is the result of years of research and testing, multiple prototypes and a ground up redesign of the original ground breaking "Corsa Veloce" product range. Available in two major configurations they feature a full billet plenum with generous billet bell mouths and thick wall polished CNC mandrel bent tube components. High end TIG welding assembly makes them suitable for up to 100psi boosted applications. No other product comes close to this level of strength and detail.
The plenum volume and runner length combination has been selected for aggressive low and mid-range torque while opening up power higher in the rev range. The plenum volume is large enough for serious gains but is still compatible with factory AC. The Street version is suitable for any level of performance modification as they have conducted tests on completely stock engine/turbo/fuel system setups with approximately 9% gains in torque and power level, with the same percentage gain on highly modified setups running E85. For a fully streetable but aggressive setup while retaining the comfort of AC, the Street version manifold is the solution.