My cousin has a 1997 300ex, full curtis sparks pipe, uni air filter...Were not sure if anything's been done to the motor or not. But it hasnt even been rejetted for the pipe and it will walk all over my blaster. My blaster is all stock with wiseco piston & ring, boyeson reeds. When I grab 5th gear on the 300 that damn thing is gone, it's fast!! lol...