Do you even know what a Snap-on fuel care machine is, or does?
I did it to my '07 Nissan Titan with 85,000 miles on it. It cleaned the injectors, intake valves, and even helps the converters and O2 sensors.
How do I know this is true? I have a very nice little scanner that can read all kinds of fuel trim and air/fuel information as well as all the other systems on the vehicle.
When my fuel trims were a little off from one bank to the other I knew it was time to hook up the fuel care. After 15 minutes of running on the fuel care my fuel trims evened out and everything from bank 1 to bank 2 is pretty much even like it should be.
This is probably the only time I'll ever use it, because once this rig is paid off I'll be getting a newer one. The fuel care machine is not about "upper lube" either, it's about cleaning. Upper lube is supplied by the engine oil, and the valves and valve seats do not need anything. I probably could've let the truck go into eternity without any problems, but the machine was there to use, why not use it once.