ATP's GT3071R is a great match for the 06+ WRXAnd 04-09 STI's 2.5L engine, especially if you're looking for boost threshold that is close to stock but want enough airflow for 450+ hp. Almost all the boost is available all the time; even at part to medium throttle!. Boost recovery between gearshifts is awesome with full boost ready even before upshift is complete as the STI lurches forward with shear enthusiasm at the onset of each gear. If you have a built 2.0L and are shooting for 450+ hp, this turbo will work, although it will have significant lag. The modern generation of Garrett wheels, coupled with an awesome wheel ratio, allows even the smaller displacement EJ20 engine to provide adequate motivation to get the GT3071R going for a great powerband. The 3071R competition-grade turbo still offers the best response and spooltime out of any unit in this flow range. The GT3071R uses a 60mm 84tim turbine wheel and 71mm 56 trim compressor wheel.