I've been having a conversation recently with someone about high mileage 4.2V8 engines (such as you get in the B7 S4). The other person is telling me that 'they have been told by an Audi tuning specialist' that the aluminium engine blocks used in the V8 are specially treated to 'withstand the stresses of being an engine block'. OK I think. Apparently this treatment starts to 'break down' at 100k miles and causes issues in the block and cylinder. - I have never heard of this phenomenon, so thought I would throw it to the wisdom of the internet (rofl) and see what opinions came back. I'm familiar with cam tensioner face issues on this model, but not much else on the V8.