[cewillis]

I have a 96 with a similar problem. Not sure if a 90 has similar wiring, but on mine, the black wire from the throttle potentiometer splits to provide input to a micro switch controlled by F/R switch. In forward, the signal goes straight through to the controller. In reverse, the signal goes through a 1/2 speed reverse resister?? (is it a resister?), and then to the controller.

I know the resister?? is bad, because I wired around it, and now have full speed reverse.

Question: is that a 2.5K resister? That would make the reverse throttle signal 7.5K to 2.5K, instead of 5K-0.
The reason I ask is it seems that arrangement would only provide 1/2 the useful peddle travel.