I too am plagued with this issue. Why GM went to a computer controlled throttle is beyond me. Maybe a cable actuated throttle fails too often.
Of course, I did the Dorman TPS. (Mistake) and threw a connector and APPS at it. Still no luck. I recommend buying a Tech 2. Are they expensive for a diagnostic tool? Maybe. Depends on if you are going to be working on your vehicle long term. Eventually, they will pay for themselves in spades. I will be purchasing one when funds permit to tackle this issue.
Current plans to remedy this before Tech 2 purchase are;
New ACdelco TB, clean up engine and body grounds, see if the problem is fixed.
Could the TAC module be bad as well?
