Off idle bog
Sounds like your 2 idle fuel ports are plugging off with gum from old fuel.
Back the 2 idle fuel mixture screws all the way out, spray some carb cleaner in them a few different times, maybe even run a small parts tag wire in them to help clean them out.
Polish up the ends of the adjustable fuel mixture needle screws with a scotch brite pad and carb cleaner. Then rinse everthing out with carb cleaner and blow out the idle fuel mixture ports with compressed air.
Reinstall idle fuel mix screws 1 1/2 turn out from seated, warm the engine up good them readjust the idle mix screws to get it right.
Good Luck . . .