[stewy604]

Does it only shake when you're off the throttle, or all the time? From your OP, it sounds like its under coasting only? How do you know its the engine that is shaking? These vibrations are typically a tire/wheel/balancing issue. I would start there and ensure you've got properly balanced wheels (also check for bends). And then work your way "up" through the powertrain. These wide wheels can often be difficult to balance.