Im new to Polaris ATVs. Up until now i was always a kawasaki guy but decided to try something new. I own a 2008 Polaris 500 H.O. EFI. It was performing perfect up until i got it out of the building the other day. The atv had performed perfect on the previous ride and showed no indications of breaking down. Then, i got it out of the building and started it, the atv revved pretty high upon starting then went very low in rpm's and died. It did this repeatedly. It runs fine as long as im on the gas steady, but as soon as i let off it tries to backfire and eventually shuts off when it hits low rpm! any suggestions?