Hi as far as I know, the long timing chain can get stretched with the higher maintenance intervals and the number of chain links between the drive gear and bank 1 is longer than bank 2, affecting bank 1. I do not know how to check the chain without disassembly. On my previous cayenne turbo 2004, it was repaired on warrantee. On my current 2008, haven't had the problem and am more careful to change the oil more often...