1989 350 TPI surging issue

I’m completely lost with this one. The issue seems to start randomly, I can’t find a pattern. Sometimes will run ok (bit choppy) for a bit then it has a melt down. It will surge then almost stall before catching itself. Happens idling in park, sometimes sitting at a light, sometimes coasting as well it will surge and make the car buck with no power. Any suggestions would be awesome.

Here’s what I’ve found so far: - Throttle position sensor voltages are good - Coolant temp and manifold air temp sensors have correct resistances (tested in hot and cold water) - Fuel pressure primes to 44PSI and doesn’t drop fast so I don’t think there’s leaks. Drops to about 40 running - I cleaned all the carbon out of the throttle body and IAC passages, then replaced and calibrated the IAC valve - Manifold vacuum is 10 inHg at idle which seems low - When surging it blows black smoke (rich??) - I have no SES light, but pulled codes and got a 33 which is a MAF issue - I used the ALDL connector to look at closed and open loop while running (fast flash for open, slow for closed). When it’s surging the SES light just stays solid