Can't see the point tbh, only really applys the direct injection engines in my eyes. The port injection on the 4efte continually squirts petrol down the intake ports of the head, which naturally cleans carbon. But if your bothered about any other parts of the engine I.e exhaust side, if that's got an excess build up of carbon that's probably due to fueling problems which need to be sorted prior to the cleaning or it will build back up again immediately