its just a set of pedals for the stock reed cage. then they have the rad valve whihc is made by the same company and lastly the V-force reeds. I have the v-forces and they add throttle response but from what I have read and been told before they only make 1-2 hp on a modified(ported) engine so they are really just a throttle response modification.

I bet those reeds in the stock cage with no reed stuffer would be nearly as good as the boysen or the V-forces just my 2 cents, but I have no indepth data to back that up.