Quote Originally Posted by Charlie View Post
the label says "REMANUFACTURED BY GM CORP. SERVICE NO.16236757"
This is a remanufactured PCM, not reprogramed.

This does not seem like an aftermarket tuner company to me. This could explain why you did not feel any difference in swapping the two PCM's.

The label explains it, it states remanufactured, and not reprogrammed.

Just my take on it...

You have two PCM's for the car, one could be faulty.