1991 suburban rough at minimum throttle

I have a '91 suburban (1/2 ton, 5.7 TBI) starts,idles and revs great, stumbles at most minimal throttle(parking lot speed) replaced cap, rotor, plugs, wires, filters. Ran injector cleaner thru it, swapped TBI with a known to be working unit… I’m lost!! HELP!

Cleaning the mass airflow sensor comes to mind as a worthwile inexpensive thing to try.

No mass air flow on 1991

Did a parts search and it seemed to be out there, good catch. Have to revise to bad injector, 02 sensor or pcv valve as my wag.

Anyone else got any ideas

Check the timing and TPS.