Diagnose - 2,500 rpm Stumble Miss - 1991 8k mile ZR-1

[SteelBlueZR1]

Thanks for all the feedback... Since the stumble and hesitation, followed by rough running and loss of power from 2,500 rpm up was intermittent, everything I did seemed to help, but then the stumble returned.
I just replaced the fuel pumps with OEM AC Delco's, and the stumble hesitation continues, but the pumps did test weak, and now the car starts in 1 second or less vs. 4-5 seconds with old original pumps, plus the power key off drivability is improved with new pumps.
I am just driving car in power key off mode, but really want to solve the problem. I will have WAZOO help me diagnose with Tech 1, before throwing more parts at it.
I did pull codes and had a 61 -low secondary port vacuum system pressure. I checked the secondaries operation, using Haibeck's probe the pink/black wire at the ECM with plenum on instructions, but my car battery died during the test, so it was unclear for now if the secondaries are opening properly.
I am thinking the Secondary Port Vacuum Actuators are bad, and/or the Secondary Port Control Solenoid, and/or the Secondary Port Vacuum Reservoir, but only a plenum pull and vacuum test process will answer this ongoing question.