I had an instructor in high school auto mechanics who taught me the " cup of water at fast idle trick ".
Obviously , it was a carbureted application , but feathering the throttle at the carb while slowly pouring a cup down the venturis.
He claimed it steam cleaned the chambers and valves.
Since nearly everyone was driving junkers back then , it got tried often.
I wouldn't call it tune up in a can , but it did make a difference with a lot of them.