yea, def depends on the car... My previous motor had those heads, box stock 6037's with a cobra intake, and a pretty simillar combo (of course without the blower) and it put down a tick over 300 hp, and close to 340 ft lbs at the tire, the car went 112 mph all day long full weight. The performers are a strong head if used in a good combination... but like everyone else her has said... It takes a really good combo, and LOTS of tuning to get there. With a fully built motor, and a decent H/C/I 300 rwhp is easlily attainable these days...