i think on some applications(advanced ignition timing ,portwork,carberation) it is not as noticable to some people and will yeild different results just as pipes,carbs, heads , and dyna FS programmable boxes will do ,i can safely say it wasnt in my head , it isnt 5hp+ or anything,but noticably faster revs off idle and it does hit the pipe a tad sooner in MY experiance. i dont consider this mod a gimmik by any means and it was worth the money to me ,to each his own