The Rattle could be the Vacuum Pump Failing. If you want to pull it off and inspect the Arm and Bearing and the face of the Fuel Injection Pump Timer.
What in particular causes vacuum pump failure?
What in particular causes vacuum pump failure? - PeachParts Mercedes ShopForum
New Vacuum Pump Ruined due to too much Timer/Intermediate Shaft End Play (the title from my notes).
second vacume pump, help! on a trip-Toronto - PeachParts Mercedes ShopForum
On mine I had a rattle at the Front of the Engine and it turned out to be that the upper most stamped Sheetmetal Timing Chain Guide; the one that you can see if you can see on the drivers side of the Engine when you pull off the valve Cover was loose and rattling.
The Air Filter support and the Studs have been know to cause all kinds of noise. When you are driving the noise can sound like it is comming from different places.
This is not likely but Hunter had a photo where he visually inspected the whole length of the Timing Chain by turning the Engine by hand. He found some of the Pins on the Chain had backed out.