I believe you have been adjusting the idle air bleed, Paul. It is in series with the idle jet, and is strictly a very fine tuning adjustment of the idle mixture. In other words, it does not seem relevant to your current problem.
Can you put the right angle fitting (elbow) that goes on the intake side of the carburetor, in place without the air cleaner box? It works without that elbow and the filter box, but doesn't work with them, so there is nothing wrong with the carburetor, there is something wrong with the elbow and/or filter box.
