You ended up on the same path I took with an ONAN carb. I made several cleaning attempts and couldn't clear it up. Took it to a shop. You paid about half what I did, but I was as grateful as you are, and it took an ultrasonic cleaner to get it done. They called it a "rebuild" but that was years ago, when there were still some kits available. I could tell right away that the carb was better, but there was still a slight surge. Several steps down in the surge troubleshooting was "replace governor spring" and I decided to jump to that for $3 without all the other steps first. It did the trick.
GLAD you're enjoying a nice-running genny!