There are some shops that do Fuel Injector Refurbishing. Bassically they can do it on the car or off the car, (off the car is cheaper) they hook them to a machine and sonicaly clean them, usually around 30-40 dollars per injector. Alittle more expensive then trying a fuel system cleaner but they really dont do much, they are mostly all pretty much the same chemical since the amount of chemicals they use is regulated by the federal government. Pretty much haveing them "Refurbished" is a last resort.