I recently purchased a '11 Polaris Pro 163". It's completely stock. My first two rides out this year it was running strong pulling 8050-8150 RPM, Today we were boon docking pretty hard and by the end of the day it would bog and then pull 7400 and drop to 6800 and back up to 7400. This sled has 1700 miles and I'm running the premium Plug with non ethanol fuel. I don't know much of the sleds history because I bought it form a dealer. It seems to vibrate more than I remember at low RPM. It runs fine up to half throttle after that it acts up. I wish Polaris would spend some money on engineers to get this 800 figured out.