We use the machine at our dealership. If a car fails a smog or has driveability issues with high mileage it is an option. We hook up the machine to your fuel system and disable the fuel pump. Kind of like when they do a bypass on hearts. They bypass the fuel pump and run the fuel system through the machine. I usually run the car for about an hour... hour and a half depending. We use a snap-on cleaning agent that is a fuel injector cleaner and a carbon deposit cleaner. It does work... but it costs a few dollars. The best way I think to clean carbon build-up is to take off the heads and clean off the pistons and valves. If you can do it yourself great... if not wait till a head gasket blows or you do a rebuild.