double check the pilot jet orifice that one is TINY, and or bump them up one size. How does the slide drop test do? run it into that bad stumble hit the kill switch pull the plugs what do you see? need to find out if you are going lean or rich. I've found that BS34's will idle even if the float valves are leaking like sieves.
Boxes, air boxes. I find my stock carbs run best when they are sucking through the factory airboxes.