Carboning up, particularly inlet valves seems to be a pretty big problem on direct injection petrol engines, and VAG are some of the worst. My brother just got rid of his less than two year old Skoda for this and other reasons to do with its reliability to date, he is getting a Suzuki Vitara as a replacement - I know Suzuki make good reliable engines but am a bit concerned where the actual cars are made* (they have a tie up with Maruti in India that makes some models). Modern clean refined fuels were supposed to make decoking a thing of the past, and I am convinced that a vehicle that is never revved much may still suffer from it, and I put my trust in Italian tuneup and regularly going past 3000 revs as a means to keep engine and CAT healthy.
*checked and the Vitara is made in Hungary.