If you have experience in these matters,then you can do anything you want. But if you don't go into the engine, it is highly questionable if you can make it any better than the factory tune.
>Your symptoms are lean running, and although you stated that the choke system works, that is only the beginning. And if you cannot tune the choke, I highly recommend you don't start tuning anything else either.
> when beginning a tuning program, always ALWAYS start with fresh fuel, known to be free from contaminants and moisture.
> if the car also has issues when warm,then FIX THOSE FIRST. Do not try to fix a choke issue until the engines runs perfect when warm. Make sure that; 1)the valve lash is correctly adjusted,and 2)the timing systems are functioning correctly,and 3)the fuel level is correctly set,and 4)the low speed circuits are functioning as designed,and 5)that all the vacuum hoses are 100% attached and in good shape; ALL OF THEM, and 6)all the other systems are functioning correctly; like the EGR,PCV,Vapor canister and tank vent,the Thermactor flapper in the aircleaner, the heat stove, the heat-riser valve if you have one, and 7)the engine starts properly when warm. You want to hear click-vroom, the engine barely turns over and then it is running. Long crank times means something is wrong. If you have to assist it with the gas pedal something is wrong.
> You cannot fix a choke issue until the engine is otherwise running properly.Well you might be able to depending on what all else is going on.But if you then change something else, then you may again have cold-start issues.
So Then, once that is out of the way;
>Close your vacuum break 1/32 , and drive it for a several cold-start cycles. If it seems better but still has symptoms, close it another 1/32. And so on.
If it gets worse; Put back what you took out, and add 1/32....And so on
If it never gets better there are still other issues.
The carb wants to see heated air as soon as possible, so make sure that heat-stove system is working!
Good luck