Raylo

I dunno, dude. Perhaps it's the car's computer? If you could find another one to swap in that would be an easy way to test that theory. Again, I'm not sure exactly what kind the 1991 3.1 has but used ones seem to be readily available for LT-1s so perhaps you can find one.

Another thing I had happen once was the air intake boot gapped a bit where it attaches to the throttle body after some routine maintenance. Since air was bypassing the MAF the computer saw no or little air and cut off the fuel. Also, the rubber was fluttering. So the car ran rough and had no power. So check the intake path (and manifold) for any leaks. Wouldn't hurt tolook at all the vacuum hoses and connections, too.