One way is to disconnect the various components and see what's sticky. Open the hood and look at the throttle body. There is a D shaped thing on the front that has one or two pull cable attached, one if m/t, two if a/t like you. The cables are fixed by a brass looking bracket bolted to the upper intake manifold, which also serves as the adjuster for the throttle cable (the lower one). The upper one with the orange dust seal thing is the a/t throttle vavle cable, aka the kickdown cable. If you take loose the 12mm bolts holding the bracket down, you can move the bracket and cable toward the pside and get slack to take the metal cylinder on the end of the cable out of the hole in the throttle quadrant. Mark the position of the bracket so you can bolt it down in the same place and don't need to adjust the TV cable tension. The hole in the throttle quadrant on the TB that the cable ends go into has a slot, and you rotate the cable end cyliner so the cable slips thru the slot and cable and cylinder come out to the front. Now pull the TV cable end out of the cable. It should come smoothly out against mild spring pressure less than two inches to a stop, and return smoothly and quickly on release of the pull. This tests for TV cable binding, the most likely cause.
Press the gas pedal, and the action should be smooth and easy, slightly less effort than with the cable connected. The gas pedal will probably come back up fine but the cable is no longer under throttle quadrant spring tension, so it may not extend when the pedal is released, but should pull out from the engine end, pulling on the end cylinder, with minimum force to a stop. This tests both the gas pedal motion and the throttle cable.
Now rotate the throttle quadrant CCW. It should turn smoothly under spring tension about 1/4 rotation, and snap closed when released. This tests the throttle body butterfly and shaft for binding.
Reinstall the cables to the throttle quadrant and bolt the bracket back in place. If you can't get the throttle cable bracket exactly back in place, you have to readjust the throttle cable first, then the TV cable. loosen all the bolts on the bracket, and slide the bracket back and forth to let the throttle close tight against the stop screw, with about 1mm of cable slack, just loose from tight. Now, loosen the two 12mm jam nuts that hold the TV cable to the bracket so the outer threaded cable cover end has some side to side slack. Pop off the orange rubber cover and slide it toward the pside. There should be a small brass piece crimped onto the TV cable inner wire. Adjust the threaded barrel back and forth in the bracket until the crimp end is 1mm out of the threaded tube when both jam nuts are tight. This sets the proper a/t throttle vavle starting position, which means that upshifts and downshifts happen at the right speed, and that the various tranny clutches and brakes have enough apply pressure for the power being generated by the engine. The tranny can fry if this is not right, but it's easy to get right. In fact, if you feel the upshifts are early and downshifts are late, tighten the cable (say, crimp 2mm out) and see how that feels. It is rather sensitive, so small adjustments work best, under 1mm at a time for sure.
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