AFR misleading? Plugs tell a better story?

Mattax said
Does the stumble go away with a 1/4 turn more, or a 1/4 turn less of the idle mixture screws?

Some how I missed this. Would have been a good thing to try/check.

Mattax said
What is the timing at at 850 rpm? and what is it at 950 and 1050?

Will check this out and see what it’s doing.