There are MANY more ways to make a car fast besides the engine. Once you get it super tuned just right, move on to the rest of the car. It's the car that's most important anyway.
No kidding about making it fast...the engine is only about 1/4 of making a car "fast"...nothing like seeing a guy at the track with a car you just know makes over 450 hp only pulling a high 13 because it's not geared correctly or can't get traction.