Well that depends on how you set up the rest of the engine. If you just slapped on the turbo with no injectors or FPR, you might gain as much as 50 hp. But if you wait and get an intercooler, FPR, bigger injectors, bigger exhaust, etc, The sky is the limit. My 2L 16v engine in my rabbit is putting out approx 380hp and 390 ft lbs of torque at 20 psi. At 8 psi, where I have i the boost set on the street, I'm getting maybe 270 hp, but in a 1900lb car it's still not driveable in the rain. Now if all you want is a street car, putting a turbo on a stock engine will give you a fast fun car, but it will not get you enough to take a sti or even an srt-4. Bottom line, don't skimp when you build it.