I hear Megacycle makes a nice cam for the 550 but doing a nice hand port and polish of the intake and exhaust ports is always going to be the best bang for your buck. Some people stray away from doing something like that themselves, but in reality, it's pretty hard to #$%* it up. Also, a good tune up (i.e. spark plugs, wires, points, condensor, valve adjustment,oil change, tire pressure) can really improve a hard ridden bikes performance. Hope that helps.
Fox
