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.

[SteelBlueZR1]

Update: we ran the Tech 1 at a Wazoo Carlisle get together (thanks Kevin!)... and it diagnosed a bad secondary solenoid switch. switch likely damaged by backfire from bad Map line.
So after doing my first plenum pull and replacing the the Secondary Port Vacuum Solenoid, and my vacuum resorvoir, tested secondaries and my car runs like a champ; the intermittent loss of power and rough running over 2,500 rpm is now a distant memory. I think the bad MAP sensor hose caused a backfire that damaged the selonoid.
Thanks to everyone for their help.

[VetteVet]

Glad to see that you got it resolved!

Jep