Fuel additives are pure fiction. If you have really built up carbon deposits, a drop of chemical rushing by in your fuel system is not going to dislodge it. Many many tests have been done and this myth is busted. Clogged injectors needs to be removed and forcibly cleaned.
Fuel System Cleaners - Fact Or Fiction - Import Tuner Magazine
Besides, if you are running premium fuel and driving the car, the odds are pretty good your injectors are just fine anyways.
Total hype and marketing.