Best thing to do, would be to buy an aftermarket exhaust system, either complete, or just the muffler, a complete one would be better, as the header pipe is usally a bigger diameter. There are many brands to choose from, and varying prices. Put the exhaust on first, then worry about the jetting. Ride it first with the new exhaust, it may not need re jetting, depending on the brand of exhaust, the supplier should have the specs for any re jetting if needed. Mabey one size bigger on the main jet. Also, for extra performance, you need to alter your air box, or air filter system. A bigger exhaust will require more air flow intake to be of any use. Apart from that, it will sound great.