Actually, the timing chain guide that wears catastrophically is the one for the tensioner.
You can access it by removing the Vanos and the exhaust hub.
Mine was totally frazzed at about 120k miles.
I took pics, but I can't find my thread.
Another common S54 issue.
10 seconds on Google found:
http://forum.e46fanatics.com/showthread.php?t=1003185