I have an 03 Sierra with the exact same problem, and the dealer cannot duplicate the concern. However, when you lose all throttle control on the freeway, it is not a "good thing" !
They wanted to throw a new throttle body at it, as the TPS is not available as a seperate part. I showed them the post about the wiring, but they said the wiggled the wires, and could not duplicate the code/problem.
They also said, I may need a new TAC module.
I am convinced they are just throwing parts at the problem.
Any advice?? Anyone else had this problem??