I had a similar situation but, the wire connectors were a little loose. I saw where it went into and out of "Throttle Closed" in my data log. I bought a "Genuine GM" one (ACD 213-895 MADE IN CHINA! ) but didn't have to use when I felt the loose connection.A "new" TPS from the treasure yard fixed me right up. With the engine simply idling, I saw the TPS voltage jumping about a tenth of a volt.
Note: Remember they had 2 different TPS connectors - earlier models were a flat 3-wire where the newer were round 3-wire. I have a newer Throttle Body with a flat to round adapter.