Still fighting with my 84 Z28 with 350 conversion, carb, stock (correct) ECM from 305HO, 700R4, air pump removed and all lines capped, new Qjet (pro rebuild from 84 Z28). Here's whats happening: Very poor throttle response when in gear, better in park, qjet has been adjusted and appears to be working properly. Kicking down at any speed and flooring it actually loses power,running a little rough, bogs, can hear qjet gasping. No choke control, no fast idle when cold, doesn't appear to be any dist advance happening, but I don't have a light to check it. Disconnecting carb from computer causes some change, actually better. So..I completely disconnected the computer..unplugged both cables directly from ECM. To my surprise the engine smoothed out, the choke is working and the fast idle is back. Still have power loss but not as bad, carb still gasping at full throttle but car speeds up well at 1/3 to 1/2 throttle. Also tranny is kicking out(appears to be neutral) at full throttle when carb gasps. I can, with the ECM disconnected, at least accelerate slowly to any speed I want, couldn't do that before, always died off when tranny downkicked at 1/3 throttle. Is it a bad ECM? Should I have the ECM from the 85 Suburban 350 700R4 carb..or something at least from 350? Car has intake and distributer from 305HO. Airpump is only thing disconnected. Has stock exhaust thanks for any help bruce

From your description the carb needs to be adjusted. There is a dwell connector that you can use a DVM on to adjust the proportional solenoid on/off levels.
The "no high idle" is the adjustment screw that is on the stepped cam pulled by the choke control.
When cold the choke linkage will pull the cam to a higher step to open the throttle blades.
Your vacuum advance is probably connected to a variable vacuum source, move it to a constant manifold source. (some people do it others like ported vac, I've always run direct)
Confirm your base timing with the bypass unplgged and bump it up to 8-10* until you get the smoothest running.
HTH