So a neat trick, on obd1 you can run what GM called field diagnostic mode. The only info it provides is if the computer is in open or closed loop. Useful for trying to narrow down issues that are fuel mixture related. Just jumper the A/B termibals on your ALDL and drive. The check engine light will blink super fast for open loop or blink slower for closed loop. see if going in or out of closed loop coincides with your issue.