There is a little plastic rubbing block or guide that the timing chain rides on and from a combination of age and low oil the rubbing block can crack and fall apart. This causes the timing chain to ride on the metal part of the tensioner.
If you have questions need parts visit us at www.DoylestownAutoShop.com
You can send us your engine and we can replace the chains or rebuild it if necessary.
If you have bent valves and the guides are damaged Audi does no sell valve guides but we have custom guides that we had manufactured for us and can install them in your cylinder head.
Doylestown Auto Repair
241 Harvey Ave
Doylestown pa 18901
267 279 9477