I have an 09 Mule 4010 gas engine. I bought it from an older lady who didn't use it for a year or more. It will crank and run at slow speeds about half throttle but will backfire and not run if I press the pedal all of the way down. I drained the fuel tank and filled with 92 ethanol free. I checked all of the air filters and they are all really clean. Also checked to be sure all fuel hoses are clear and not blocked. Starting to wonder if it's not the fuel filter or fuel pump? It runs fine at idle and real slow speed but not when under load. Thanks for any advice!