Misfire

Have a misfire and cannot locate the problem and need help if anyone can.
I have not hooked computer up to it because it’s the old obd1 system and only have the obd2 computer.

I have changed distributor cap and re-timed the distributor, changed all spark plug gap at 40, changed plug wires, map sensor, changed oil (doesn’t affect this) and going to change fuel filter in morning, but have a feeling this is not related to issue. Could I have a bad coolant temperature sensor? Bad head gasket? Bad fuel injector? Am I missing something? Please help don’t want to keep pouring money into it to find the issue by changing parts blindly. No leaks or weird noises (besides missing or small back fire).
Thanks for help.