Be honest with you, I rode gnarlies, and fattys, and they both hit the same, I couldnt tell a difference. The T6s have a different curve, youll notice a little bit, but it's not really better or worse. The only FMFs that pull different are the SSTs, they have a little more up top. FMFs are not top end pipes. Youll see a little improvement there, but they make most of their power down low.