Throttle postion sensor problem, Please help!!

I have a 89 trans am GTA with a 5.7 tune port motor. Im not sure what the throttle sensor is supposed to be at WOT. at Idle im a .5 volts. but at wide open throttle its only 1.27 volts. I thought it was supposed to be at 5 volts. The car starts and runs fine but if you drive it around it feels like some thing is holding you back. could it be a sensor or maybe something Im not thinking of? Thanks for your help

yeah, should be anywhere from 4.5 to 5V at WOT.