The RS4 was the first major production car with direct injection and suffered from carbon buildup more than most other Audi vehicles. From the past seven years I have been following the attempts to prevent it on those cars - from catch cans to chemical cleanings etc. No one has found a good way to prevent it (other than having the engined designed to also have a injector in the manifold).
I kind of look at it as having a timing belt that needs to be changed - mechanical cleaning seems to be the only way to take care of this issue.
That said - BG makes the best products for our vehicles and I know the BG44K on the non direct injection vehicles did a great job on cleaning the fuel systems.
Edit: As opposed to the advice given on the following post - all my trips are short ones - the engine never gets warmed up. I have 33K so far and no check engine light. I am resigned to get a carbon clean in the next year though.
Last edited by Reggie; 08-19-2014 at 04:13 PM.