havn't been around here in a looong time.........anyway, i have the 421 and it pulls like a freight train, power everywhere. Im having electrical problems right now (right cylinder not firing) but besides that its completley reliable. Even only running on one cylinder its still as fast as a blaster . If your looking for a comparison, my friend had a YFZ piped, K&N, and cam and i beat him like he wasn't moving.