Oil residue air intake near throttle body (w124 m104)

[optimizer]

Hi there,

I noticed today that there is some oil residue inside the air intake (just before the throttle body). It seems to be coming from the 2 mounting holes in the air intake plastic part that sits on top of the valve cover (so seems like oil from inside the cylinder head is escaping from the 2 mounting holes and into the air intake).

This has left a thin film of oil reside all along the inside of the air intake right into the throttle body.

I can't remember and / or imagine this is normal so any ideas on what's wrong?