Super Six Idle Issues... Bit 'O' Help Please!

When the throttle shaft bushings get worn, usually or often the throttle-arm side is worse. This allows the transfer slot exposures to park differently between them, and may or may not close one throttle more or less than the other, which screws up the trimmer flow. The intake has an open plenum so it don't care about this.
This usually only makes a difference when you crank a lot of idle timing in and the butterflies are too far closed, and/or somebody is trying to run the Vcan on manifold vacuum. When you do this , you are bound to create a tip-in hesitation, as the transfers cannot respond fast enough. So then your solution is to fatten up the pump-shot..... and then maybe you can't figure out why your slanty gets such rotten mpgs around town.
If your slanty is stock, you will be hard pressed to improve anything by advancing the idle-timing.

My solution is to put the T-slot exposure back where it belongs, which requires an idle-timing reduction back closer to "normal". Then I fix the distributor and change the rate of advance.
Doing it this way, those bushings can be really sloppy and the engine runs just fine. Because in the grand scheme of things, the air entering there is miniscule compared to what the PCV is drawing.