Here is your awnser greencrew... I do about 4 "injector" cleanings a week. We (and most dealers) use a machine called a Motorvac. That is the most common machine, but there are other machines that do the same thing. Here is what we do, procedures change from shop to shop, and I think our service is the best way to go. First I unhook the fuel lines, both pressure and return (depending on model, this can be done in the engine compartment, or under the vehicle, forward side of the fuel filter), I hook up a T into the pressure side, and a a straight hose hooking the return line back up (this is done to do some tests), then the vehicle is started, specail solvent is put into the machine. Running pressure is recorded, and then the return line (on the straight part I installed) is pinched off momentarily to see max fuel pump pressure, which is recorded. The vehicle is still running, and I push a "Fill" button on the machine, which pulls fuel from the vehicle, this also checks for flow from the fuel pump. This first part of the service checks the fuel pump, fuel filter. Then once the machine has the correct amount of fuel/solvent mixture, the vehicle is turned off, the pressure side hose is looped to the return line, so the fuel pump is just pumping fuel back to the tank. I then hook up my pressure and return lines from the machine too the vehicle. The machine is capable of 120 PSI. I then turn on the machine, and from their, the 120psi is regulated by the vehicles fuel pressure regulator. (40psi or so depending on model). I leave the machine running for 15-20 minutes (vehicle off), the machine actually pulses the fuel, which results in debris being pulled up out of the injector screens and pushed back to the machine, which has a 5 micron filter. Fuel filters on vehicles on filter down to 20-30 micron. This is done to clean the fuel rail, and any debris that me be stuck in the injector screens. After that, the vehicle is started and ran for 60 minutes. Theres more that we do, but is not relavant at this time. The Motorvac solvent is an Amonia based cleaner, that melts carbon on contact. This service test your fuel pump, cleans your fuel rail, cleans your injectors, cleans your intake valve,s cleans your combustion chambers. The only way to get an injector that clean, is to take it of, and have it cleaned. We usually see 1-3 inches of vacumn at idle after this service. I did my Sport-trac at 35k, started with 18.0 inches of vacumn at idle, when I was done it was at 19.5, I got better power and milage. I have countless success stories, ...2000 F-250 V-10... just tuned up by another shop, +$300 in trying to diagnose but it still had a P0300 random missfire. I hooked up the Motorvac machine, and ran it, while watching missfire counters on my scantool. After 20 minutes, the missfires were gone. I finished the service, and the truck ran perfect. That customer now brings his vehicles in every 30k for that service.