Back to the throttle response, you can try rotating the throttle down (counter clockwise) a little as long as you're comfortable with it. Maybe your thumb is grabbing at the bars on bumps, this will help you hang on without hitting the flipper harder than you want to. To check your exhaust, block off the exhaust pipes (after it's warmed up fully) and it should stall. If it continues to run, donuts are done or worse. You'll get used to the sound, and maybe wear ear plugs, makes a world of difference.