Your altitude above sea level could affect your engine power. Also check you HST lever adjustment, I believe it should come forward to within 0.040" of max. Check out the thread about HST Adjustments. Your max engine RPM should be 3200, but I adjusted mine to 3400. I've tweaked my 2010 RTV 900 to get up to 28-30 MPH. You can check some of my posts and pictures, I cut off the factory spark arrestor and installed an external aftermarket one with better flow and longer intervals before cleaning. Good luck.