I did the APPS (accelerator pedal position switch) on my 2001 many years ago. It's just a potentiometer basically, and right where you drive it wears out, so my truck would go from 0% throttle to about 8% (where I drove, then it would stay showing 8% as you increased throttle, then jump to about 18% and go up from there, so it generated a big surge as you accelerated.
I bought a replacement POT kit on Ebay for around $50, since the APPS is over $200 (was anyway). It's 3 bolts, a few screws, the throttle cable and one electrical connector and easy to do.