""Can't get it to idle correctly without sticking a tooth pick in two of the outer bleeds.""
- If you are making the IAB's smaller and getting a better idle (no other change), then you are lean and need to rotate the metering screws outward to richen up the idle circuit.
One reason for changing the air bleeds sizes would be if your metering screws are only out "less" than about 1/2 turn at best idle vacuum. Using larger IAB's would help move these outward at best idle vacuum.
Another reason would be to lean/richen (tweak) the transition circuit during cruise.