Why is my TPS reading WOT when throttle is closed?

[gramsch]

After a MASS AIR conversion and Supercharger install. My car runs like S$#T I kinda traced the problem to the TPS, it is reading 4.92 volts with the car not running and the throttle blade closed. A buddy of mine said the TPS was working in reverse could this happen? Is there a difference in TPS Sensors between the 86-88 and the 89-93 mustangs. The computer and wiring harness is from a 90 and the computer is a 9AL. Can anyone help.

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Michael "Deke" Gramsch
87'GT - Oxford White (soon to be vermillion red)
Powerdyne 9 PSI Supercharger, 30# fuel injectors, Pro-M 77mm
MSD 6AL ignition and coil, 65mm FMS throttle body, K&N filter, Accel Pro Billet Distributor, Fluidyne Radiator and Blue Hose Kit, Long Tube Headers, Off Road H-Pipe, Flowmaster American Thunder Exhaust, MAC Shifter, Weld Draglites, 190 LPH Fuel Pump, ADJ Fuel Pressure Regulator & Fuel Pressure Gauge, and some other odds & ends.