After all these years. That car still looks great.
If I didn’t have my Cayenne Turbo S I’d have a S8. Loved my wifes D3 A8 and the S8 is better overall of course. I know the later D3’s with the rear timing chains need the oil changed regularly to keep the chain guides clean and to reduce wear along with clean oil in the tensioners. Which version of the
Cayenne Turbo S is a great choice! It was on my radar as a candidate for my next vehicle when I decided to retire my B5 S4 to the weekends. It seems like many people go from B5 to the Cayenne Turbo S. Ultimately I found the 2007 D3 S8 and am so happy I did! I am unsure of the timeline for when Audi started implementing fixes/material improvements from the factory floor on the rear chain guides and tensioners. I know from firsthand experience of a 2008 3.2 A6 that had failed upper timing chain tensioners.
It would be interesting to crosscheck the part #'s between the B7 & B8 S4’s compared to the later D3 A8’s as the B8’s definitely had a better reliability with the timing chain & adjusters/guides. I know they say long interval oil changes and lower grade oils have a lot to do with it. You want clean oil and good lubricity to extend their lives.
Did a little bit of maintenance on the S8. I have been putting off replacing my valve cover gaskets, but as I was coming up on an oil change I figured now would be a good time. They were starting to leak a bit more and drip onto the exhaust manifolds, which does not smell the best.
The old gaskets really needed to go - very brittle and no longer doing their job. I also used a little bit of LOCTITE Automotive RTV Silicone Gasket Maker Black 598 on the corners. Easy enough to do, especially if you have done this job on any other audi. As stated on other threads here, having a mini ratchet is very helpful for the rearmost corner bolts for the valve covers. Just take your time, clean up your mating surfaces, use a 1/4" drive torque wrench, and you will be good to go. I drove it up to temp after all the maintenance, and then changed the oil. Just a best practice after having brake cleaner around the open valve covers.
I put in new spark plugs (while I was in there sort of thing, and I am guessing never been done. They looked good but this was nice to do), BG44k fuel injector cleaner (before every oil change) new valve cover gaskets, oil change, and an engine dressing. Came out great and driving as good as ever!
If you ever thought to yourself, are my valve cover gaskets leaking? Just use your eyes 
!
All better!
I used these gaskets from ECS:
I went with these NGK spark plugs from FCP Euro, which after doing some research I believe is the model number that came with our cars:
