2003 Grand Prix throttle sensor question

Advice welcome as I have replaced TP sensor with a known good and a new one - both with same results as original. Increased rpm's and throttle % slowly rises without any throttle pushed. It seems that from a cold startup and just idling watching the scanner the TP will start slowly rising until it stablizes at around 30% on scanner. It seems to start rising when the temp gets close to 170 -180. All this without any throttle being applied. I have checked ground and the 5 volts. I have cleaned the throttle body as well. Wires all seem good. Mileage at 113,000
Any advice is welcome Thank you.

So, the tps data starts to rise, even though the throttle plate doesn't move, and rpm's increase?

If the tps data/rpm's increase without the throttle plate moving, and the connectors in the harness to the TPS are ok, then I think you need a reflash or PCM.....

Tech II - yes the TP data will slowly start to rise until around 9% then the RPM's jump from around 800 to 1300 + all with no throttle applied. Cable connector and wires appear good no deflection when moving them and watching the meter while checking the ground and 5+. Shoud I replace the harness first or try reflashing the PCM? I have had it show a TP sensor error only 1 time with original sensor otherwise no codes stored or pending with my lower end reader or my local garages high end code reader. Was wondering if another sensor was affecting the data when it warmed up enough. Thank you