I forgot to say I run the free too, but I think I did earlier in this thread.I'm running ethanol free gas plus Echo Powerblend at 40:1 in my 261c and have for 3 years. I cut year around and the only issues I've had are hot start when the temps are 105F + (and only then when I don't let idle for a few seconds before shutoff or if placed directly in the sun for a while). I also run this in my newer 261c and my 441c with no issues.
I don't think your fuel ratio is the issue. Just my two cents...
Yesterday I was thinking about letting it run a bit before shutting it off when the 201 acted up. That's fine when they have plenty of fuel in them, and I guess I could get away with it when they run out as there is usually a good bit left, but I have a habit of shutting them down as soon as I hear them surge at. It was 45 here yesterday when I was cutting so I don't think that had anything to do with mine acting up. I don't recall having a problem like this on the later 550's often, the earlier ones would act up, but just as the 201 they would straighten out. I have noticed this on standard carb saws now and then, maybe a small bubble in the fuel line that doesn't get purged out or something, but this seems to be something separate from the OP's problems.
Those 441c sure are nice runners , and smooooth.