Yeah, as Flybox says mains won't do anything for idle. That's only for something like 3/4 to WOT. Not sure if someone posted this for you in all your threads (
just playing around) but this will give you an idea what circuits you should be dealing with for idle:
But disregard the throttle slide cutaway, I haven't really seen or heard of people changing this except for super extreme fine tuning.
If you can get it to run with choke on/fluttering then you're not 180° off with the advancer.
I see you still haven't adjusted the cam chain. It won't fix your issue, but usually you want to have everything else perfect before tuning carbs. To me it just seems careless.
What was the max amount of turns out with the IMS that you tried?
And you never posted a picture of your float levels with the clear tube method, right? I know you say they're perfect, but you also said your carbs were spotless when you never removed the slow jet...
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1978 Honda CB550K