If you are riding in the desert and sand where u can rev the 500, then u may want a little more up top. I am running an FMF Gnarly Desert pipe, Powercore silencer and a Boyesen Rad valve (more of a topend pipe). Eventually, I will switch to a Pro-Circuit 2 and a 304 silencer. Which, Ive been told will improve power all around compared to stock. Theres a guy here named Stewart who has dyno tested a lot of aftermarket pipes and reed valves. Based on his tests, the Pro-Circuit 2, 304 silencer, and V-force reeds put out the most power. If you do a search of the forum, I'm sure u will find some info about the best pipe / reed setup. Good luck