I've often thought about trying to get a cruise control actuator, like the electric operated one on mid 90's Fords, to assist the factory governor on Listeroids. They are driven by electricity and have cable connection to the throttle shaft. I can't really tell much about just how they are controlled from looking at a wiring diagram, they just show a few wires connecting the actuator to the main computer. I plan to measure what is going on in the wires with a voltmeter while driving on cruise control at some point but I fear building a control circut is beyond my knowledge of electronics. I also don't know if this actuator can react fast enough even if it had the correct driver circut but it seems like a good start.