1st thing "I" would do is dump a whole can of BerryMan's Chem Tech in less than a 1/2 tank and run it hard!!! Leave sit at least overnight with this mixture in it and in the carbs good before you refuel. Then reset idle screws and sync.
A Color-Tune is a thing that lets you look into the cylinder while adjusting carbs to see how they are firing. From red, too rich. Blue, getting close. Real light Blue or white. Too lean. Do a search on Gunnison Color-Tune.