There is an updated check valve located inside the oil filter housing that holds oil into the top of the engine and into the oil filter housing when not running. The new valve has longer fingers to hold it centered over the sealing surface. I have replaced a few of these and it solved many problems with cold noises.
I have found two sources of the noises. One is the chain tensioiner and the other is the cam advancers. IF they are not under oil pressure, they will rattle.
The valve mod is in the SI bulletins. I forget the number....
Also, the oil tubes that are between the cams have been updated with new O-rings. This is the cause of unwanted lifter noise in most cases.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS