I am way far from a mechanic, but that last statement seems to indicate that the problem would be be in the fuel supply area – something like a momentary failure in the fuel pump, or something like that?
It’s a '93, it’s pre-OBD-II. OP would need one which can connect/read the old GM ALDL.
Besides, that’s not needed; if you short two pins on the ALDL connector it’ll flash the check engine/malfunction light and give you any two-digit codes present.