It is, however on FSI engines where the fuel is injected straight into the combustion chamber, the only area it can clean are the combustion chamber, and maybe exhaust valves.

The biggest issue on FSI engines is a buildup of carbon deposits on the inlet valves due to the ingestion of crankcase vapours that carry oil into the inlet tract, that would be normally washed away in traditional fuel injection systems where the petrol was injected before the inlet valves.

Looked at that but everything I've read suggests that it's a fuel line based treatment, in other words it can only clean where the fuel goes, since the inlet manifold and above the inlets see no fuel............

Unfortunately little or no use for any FSI engine.

http://www.e90post.com/forums/showthread.php?t=682116

I thought this was interesting food for thought.......