2013 Polaris 800 RMK Pro, Starting air temp 15 deg and rose to 49. The last 25 miles the RMK began to lose power. At first it ran fine at 3/4 throttle or less, then 1/2 throttle, then 1/4. Engine temp was 130-140, no codes or errors. Replaced plugs, no change. If the sled sat for 15min, would run fine for 5 min then loss of power would start again. Other sleds were running fine. Any suggestions?