What's good to clean fuel injectors in an engine?

I have a Ford F-150 with a straight 6 cyl. engine with fuel injectors and I have try injector cleaning fuel additives and transmission fluid and mystery oil which I add to the fuel not all mix together but every full tank I will use one of the 3 in the gasoline tank but so far without success. Please advice on which is the best way to clean fuel injectors without taking them out. Thank you!