the horsepower gain from a header all depends on what kinda upgrades you already have... if its stock... you may feel a bit of a difference, but not much, maybe like 5 whp. but you will definitley hear the difference... the more you do to your motor, the more effective that header will become. and the more effective all your other mods become, all mods pretty much correspond to one another, in order to have good exhaust, you need to have good intake and so and so forth... but its a good start to a decent hp gain. -Jason