Hello, i am having what could be a bad ground in my 91 gmc 1/2ton truck. I installed a summit CD ignition box, 454tbi fuel pump, and a guage cluster out of a 95 1/2ton. I also had to wire and install a DRAC box to convert the signal coming from the VSS to digital signal for the speedo to read. Everything worked great until my crus stopped working. Everytime i would try to set it, the motor would cut out really bad, as if there was no spark or too little fuel. Then my speedo started messing up. In park if i reved it, the speedo would come up with the tach, when in gear, at low speed it pulses up and down. the faster i go the faster it goes up and down until anything over 25mph then it goes all the way to 85 pegged out. If i give it a lot of gas it will cut out as if i were trying to use the cruse again when it wasnt on. At first i replaced the DRAC, battery ground cable, swaped out the coil, disconnected the tach, vss, nothing worked. I did notice that while the vss was disconnected, the speedo didnt pulse anymore, but still went crazy at any speed above 25mph, or at high rpm. still cut out, but cruse didnt do anything when activated. The only thing i can think of is a woring problem. But i have no idea how cruse controll can have anything to do with the engine cutting out. If anyone has any ideas or better ways to find out whats wrong, please help