I agree with Accurate FI.......basically, anything you put in the gas tank is for maintenance only......it generally will not clean a clogged injector....
Most shops have equiptment that attaches fuel injection cleaning solution directly at the fuel rail, under pressure, to clean injectors.....
Only way to know if the cleaning works, is to do a flow test on each injector, before the cleaning, and then afterward, and compare.....
GM has started using direct injection in it's engines, the last few years....it will be interesting to see how long these injectors last, and how difficult it will be to remove them from the heads, over a period of time........I personally don't get it...you make the injection system more expensive to repair, and yet with the added cost of two fuel pumps, some high pressure fuel lines, is it worth it? There doesn't seem to be any huge increase in gas mileage....