AFR misleading? Plugs tell a better story?

skidmark said
Trying to tune carb and fix a miss/weird stumble at idle. Engine runs smooth once RPM’s are increased, also seems to use a lot of gas

Does the stumble go away with a 1/4 turn more, or a 1/4 turn less of the idle mixture screws?
What is the timing at at 850 rpm? and what is it at 950 and 1050?