You will get all kinds of claims to the best power on the dyno. It is hard to say, even looking at dyno sheets dont tell you much because it is a different bike at a different dyno with lots of variables. I like the Brocks for a deeper sound and good power increase.... Also the Austin Racing has a nice deep sound I hear and good power increase. Arrow is another one that comes up often. Only one I have experience with right now is Brocks but I am trying to find a way to get my hands on an Austin Racing GP3.