i have a bunch of pipes i have run off and on over the last couple of years. pro circuit, fmf woods, fmf desert and stock. to be quite honest i didnt feel a huge difference between any of them. id say the woods pipe and the stock pipe gave a bit more low end power while the pro circuit and the desert pipe seemed to rev a bit more. i ride with 3 other 500s and when we drag race none of us has a clear advantage. i have put my stock silencer on one of my bikes cuz the fmf fell apart inside. ill let ya know how that turns out.