AVS2 tuning
The clues are there....
IF the transfer slot position is correct, then idle quality should not change whether the rods are up or down. That is because there is insufficient airflow to activate the main system.
I suspect your pri t/blades are open too far at idle { big[ger] cam? }. Depending on a number of factors, low speed cruise can be off the transfer slots, NOT the main jets...which would explain why changing to smaller jets made no difference.
Another indicator that the blades are open too far is if you screw the mixture screws all the way in & the engine keeps running.
The first step in carb tuning is actually....ign. Get the correct amount of timing at idle that the engine WANTS; it will often be more than the factory amount because the factories had to be conservative. Once dialled in, check t/slot position. Also check that PCV is working. If it vibrates, vacuum is too low for it.