AudioVox CCS100 Electronic Speed Control

I have some lower extremity disabilities and I also have a Trooper T2 off road vehicle and an AudioVox CCS100 Electronic Speed Control(Cruise Control). My question is: has any one hacked one of these or know how they work, specifically, how the vacuum is controlled that activates the throttle. Presently, if I activate the controller in a lower gear, it drops out a lot because the engine speed varies too much, I assume. My goal would be to redesign it to hold a set RPM speed and not drop out except when turned of or brakes applied.
Eventually, I'll hack into it by my self, but if I can get some tips or advice,
Thanks
Kinarfi