The mixtue screws don't affect idle quality much and they don't affect AFR. AFR will always stay at about 14.7 (I measured Lambda 0.99-1.00).

The idle speed screw needs exactly one turn until the blades touch the venturi bores, or until the screw doesn't touch the throttle lever anymore.

Today I openend the MP distributor. I took out the heavy spring for a lighter one to get the mech. advance in earlier. Also I shortened the advance slots to raise initial timing by about 3 degrees and retain total mech at 34. Unfortunately time was running out and I couldn't start the engine for check. That'll be next.