white coloured valves?
At the moment doing a rebuild on a 2.0l gtv, I have noticed that it has been running lean and the valves and the sparklugs are showing a good deal of white colour from previous running.
If there was an air leak after the MAF this I would imagine would be overcompensated by more fueling and show black deposits, so the opposite seems to be happening, is this the effect of the car running on three cyls and the lambda instructing the ecu to run less fuel, and so burn lean or what.
The plugs by the way have not been allowed to run correctly because the chamber around has been filled with water for some time due to some enthusiastic pressure washing of the engine bay at sometime. It has only had a 50mile trip since, maybe not enough to change the norm, as in this case.