Something I almost forgot about. The one product that keeps A4s running forever is ::Marvel Mystery Oil::
This stuff is unreal, fixes more problems than you can imagine, and all you have to do is put a quart in the crankcase the next time you add oil, and 2-ounces per gallon in the fuel tank. It seat the vales, cleans the valve faces, cleans the seals, cleans crud off the cylinder walls and helps seat the rings. And, it doesn't take many miles on the engine to get results. I've seen A4s that everyone said would never run and after treatment with the Mystery Oil than ran like a Swiss watch.
Hope this helps,