[ZR2LIFE]

I would report them to the BBB and file a complaint with GM. I would also go to a different GM dealership for warranty work since they are clearly incompetent. You should have never been charged anything to fix the problem.

 

[ZR2LIFE]

There is another post on this forum by someone who could not get their TB above 30. Dealer found the problem to be the Throttle position sensor pigtail got wet inside and was not functioning correctly. Here is what a TPS is:
The TPS is mounted on the throttle body and converts the throttle valve angle into an electrical signal. As the throttle opens, the signal voltage increases. ... A ground wire from the TPS to the E2 terminal of the ECM completes the circuit. At idle, voltage is approximately 0.6 - 0.9 volts on the signal wire.

You can see TPS voltage clearly with a scanner and you can see if the signal is linear or erratic which would also indicate a problem with the sensor. Most TPS max out around 5.0 volts at WOT.