I agree with justin. The number by themselves is a little misleading. That kind of horsepower gain comes from working the insides of the engine. Just putting those headers on alone, won't give you that much gain. I believe the most you're going to get from them alone is about 1-2 or 2-4hp. If you do that whole port and polish, just work the internals you could probably hit those numbers. But GOD, I thought you said a while back that you weren't going to mess with that stuff, just rims and a kit I think. Regardless, I say read more into it before you spend that money and don't get what you want.