While trying to diagnose the problem, I held the governor rod to the carb steady and the rpm's smoothed out and it didn't stall or rev. Made me wonder if the issue could be in the governor rather than the carb.
The fresh higher octane fuel probably cleaned out some of the garbage trapped in the fuel system is my theory.
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The “governor” on most low cost generators is a steel flap and a spring inside the cooling shroud.
Better units have calibrated centrifugal governors inside the crankcase that need clean oil to operate properly.
Water is the most common ‘garbage’ in fuel systems, but it usually doesn’t accumulate if there is alcohol in the fuel.