We traced the TPS output wire all the way from the throttle body to the PCM. To make sure we had the right wire, we used a voltmeter to watch the voltage vary as we opened and closed the throttle. We then tapped into the TPS wire with the white signal wire from the Zex management unit. Because every car is different, the WOT output voltage is anywhere from 4-5 volts; you need to program the Zex management unit to your particular car. Once it's all set up, it will always look for that peak output voltage from the TPS and use it to activate the nitrous system.