Once again good advice is needed with a couple of engines..

I would say that you need to focus more on accelerator pump duration, which I'm not familiar with on the AFB. On my AVS, I believe you could alter the linkage rate by swapping to a different set of holes in the linkage.

And, I would say adjust the springs for the intermediate needles and try different needles.

You're talking about the transition from Idle to main jets (aka large amount of throttle) and the needles govern the bulk of the area between the two.

It IS actually pumping fuel through the accelerator pump (Both carbs), right?