Cam adjuster diagnostic
 

I'm going to be doing the timing chains and guides on my 07 Q-7 pretty soon, and I need to decide if i'm going to replace the cam adjusters while the motor is out. I've looked around a bit but I cant seem to find a diagnostic guide anywhere. Does anyone know if its covered in the Bentley manual?
The car is a 2007 Q-7 4.2, with about 150,000 miles.
Any help with this would be greatly appreciated.