k204dr said:thottle cables can be worn inside, causing them to be stiff to move when under load, but move easy when you have them unhooked. the pressure from the spring will pull the cable inside down into a groove its worn. it also could be the throttle shaft kinda doing the same thing. I'd get a new cable to start with.
DING DING DING, we have a winner. Its a bad cable, or cables. Mine did the exact same thing, I swore it was the tbi because the cables would move easily and freely when I undid them. I took my tbi off and had bushings put in the throttle shaft, didnt help at all. Finally I broke down and bought a throttle and tv cable, no more stiff pedal after that. Dont just replace the throttle cable becasue its mainly the tv cable that seems to cause this problem. If you unhook the tv cable sit and idle the truck (dont drive it as you can take care of your tranny pretty quickly with the tv cable disconnected) you will notice that the pedal feels considerably lighter. Replace the tv cable and/or the throttle cable if you can afford it and you will be alot happier. I have tended to notice that no matter what these trucks still have a realitively hard gas pedal even with new cables but it will still be a thousand times better that it was with the old cables. Also lube the new cables with a light cable lubricant before installation as you will wear out the new ones fairly quickly if you dont.