[BNaylor]

IMO the OP is just spinning his wheels. Instead of messing with the CJ2 diagnostics and not fixing the issue which is poor cooling on the driver's side versus passenger get back to HVAC basics. This issue is normally caused by a low or improper refrigerant charge versus the temperature actuators. There are discrepancies in what the R134 charge should be in various Grand Prix models from '97 and up. Many ID labels and service manual/owner's manuals were incorrect. GM has now established that the refrigerant charge should be 36 ounces on all models.

If you do not have the proper HVAC diagnostics equipment like decent R134 style manifold gauges to check low and high side pressure and do the recharge then best to take it to a pro.