My Mule Pro Fxt Ranch starts and runs pretty good. As you drive at either full throttle or almost full throttle, it will start slowing down and losing power. If you let off of the gas pedal a bit, it will actually run better. I've changed fuel filter, replaced air filter, replaced tank breather filter. So far, nothing seems to help, other than letting it sit for a bit. Then it will run better, or even as it should run, depending on how long it rests.