Probe the wires with voltmeter and make sure the voltage is at .98 or thereabouts with closed throttle. Should go to 4.7 with WOT and should do it smoothly without jumps or flat spots along the way. The voltage changing smoothly is more important than what it's set at with closed throttle. There's only three things the computer is really looking for: closed throttle, part throttle, and WOT.
If everything checks out, don't bother touching the screws. If not, you just loosen the two screws and rotate it until you get the correct voltage and then you tighten the screws back down. The TPS on 5.0 Mustangs was never intended to be adjustable. It's just one of those hyped up tips that magazines started.
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351W 89 Mustang GT Convertible
[This message has been edited by jimberg (edited 06-19-2001).]