went to dog riders webpage and watched there hill shooting videos. they smoked every thing. the only thing i saw on there quads were k&n air filter, cam mod and some really good jetting . but other than that they smoked everything with there stock exhuast systems. :O oh by the way its either the curtis sparks exhaust or the new factory 4 for my yfz. along with k&n airfilter jet kit and cam mod.