At Toyota we use Top Engine Cleaner which is a chemical that is fed into the intake manifold after the throttle body. We clean the throttle plate first and then run the engine cleaner. We remove a vaccum source and run the cleaner. Our cleaner requires that we raise the rpm to 2000 rpm as the cleaner is run through the engine. It results in a ton of white smoke but don't be alarmed. I'm sure that Toyota would not allow us to use a harmful product on engines. This service is standard every 30,000 miles on a max service.