When I got my TPS from autozone for my SVT they actually gave me the wrong one and when you open the throttle it brakes it. I ended up with one from a Crown Vic. Maybe check the voltage and make sure it is changing.
Green 2000 SVT #1166
mods-K&N and Custom heat shield, optimized y pipe, Magnaflow center resonator, DMDhttp://www.geocities.com/savinoss/Cars.html
-Wifes car 99 Mystique V6 5 spd