So you are saying that heavier throttle causes it? I would suspect low spark voltage. Bad coil wire, bad coil, something wrong in the ignition module, or LOW 12V SUPPLY VOLTAGE to the unit, caused by a number of things, including mis-wired (are you using a ballast and is it supposed to?) or other harness problems
Try separating the ignition system from the harness and 'hot wire' it direct and see if that makes a difference
