My 05 Polaris 500 has lost considerable power, especially in elevations around 7000 feet. It runs better in the desert but still lacks the power it once had wherever I ride it. In the high country, I cannot exceed 15mph going up certain hills, not necessarily the steep ones. In the lower elevations, it just doesn't have the power it should. I had adjusted the valves, new spark plug, new fuel filter, cleaned the air filter and cleaned the float bowl. This solved about half the problem but there's still alot of power missing. Should I re-jet the carb? Check the valves again? Get a REAL mechanic? Any other ideas? Thanks and have a good one!