This '91 GM truck has a Powertrain Control Module (PCM) that runs the fuel injection on our TBI 454, and controls the 4L80E transmission. Since we were swapping to the Compushift controller from B&M we no longer were going to be plugging the PCM into our transmission. However, we did need to get a signal from the TPS to help tell the transmission when to shift. If your 4x4 is carbureted you can use Compushift's cable-activated TPS. We, on the other hand, simply tapped into the TPS wires that plug into the PCM.