Don't meant to rain on anyone's parade here,but the dirty little secrete header companies don't tell you is headers really don't do much off idle to 3,000 rpm.Sure they tell you the best results at a rpm that you would be hard pressed to use regularly.Read that all the time that one header gives so many hp over another.But they are not really being honest about the results.Just some head games.Louder is bigger and that isn't the truth.