I have a 2000 Gran Prix GT with about 111K. I am currently experiencing a problem where the car will surge rpms about 500 or so. This occurs when accelerating from 50-55. The rpm surge will occur when the rpms climes over 2000. This surging will then stop if you accelerate over 3000 rpm. Might this be my throttle position sensor? Any other ideas?

Normally a bad TPS triggers a DTC and SES light. You can check it with a multimeter. One pin on the electrical connector will have a 5 volt reference signal from the PCM module. The output back to the PCM will vary from .4 volts at idle to 4.0 volts at WOT. Voltage readings in between should be linear and stable not erratic.

What is the tune up history. Spark plugs, wires, fuel filter, etc?

I changed the TPS and it fixed the problem.