vacuum leaks, if you spray starting fluid on cold engine does rpm surges up ?
have you tried a simple Master Reset after Throttle change ,on car we do , Switch from off to on ,wait 30 secs, then back to off wait 30 secs then crank up and let it idle for 2 minutes then put a load on it and let it run 2 minutes to calibrate the Throttle ,if you have no gm tech II scanner to do it with
1- Disconnect Battery Cables ( Negative & Positive Cables )you can use any electrical wire as an extension if battery cables don't reach .
do not worry no spark will happen since we took power source out of the loop by taking both cables off, by touching them we are taking all residual power off the modules to reset them as if we using factory scanner .
2- Hold cables Together for 60 secs ,then let go
3- Wait 30 minutes
4- Make sure all doors are closed
5- Reconnect battery Cables
6- Lock & unlock the vehicles using the key from driver door side (if you have a key fob with no blade key, just lock & unlock using the key fob buttons)
7- Enter the vehicle and attempt to start