In the real world of keeping an old truck running a few more miles retrofitting a pre feedback carburetor and distributor is preferable to driving with the feedback system operating at base time and full rich but at this point the problems can’t be isolated using system specific diagnosis. You may be forced to make the best of what you’ve got.
The year to year variations of Q-jets for all the various applicaions somtimes left off this choke pull off
which mounts at the front passenger side of the carburetor at attaching points that seem to be on all Q-jets regardless of using the pull off. Once mounted there is no linkage connecting the pull off to the choke, only the actuator that pulls back to open the choke with an easily adjusted push rod.
I’m not there to see and hear your engine run and verify that all the vacuum connections are correct, and take note that there is no vacuum diagram available for your patched up engine, but if at cold start up the engine seems to run somewhat rich and idle rough but then improve significantly when giving some significant throttle the pull off above may improve your situation. Of course that pull off may already be on your carburetor and need adjusting and properly connecting it to vacuum.