Have you conducted a proper vacuum test on the vehicle?
A full emissions test? And not from the tail pipe either. From the engine compartment.

Codes are sometimes not thrown. I am not a mercedes mechanic.

Get a pin to pin check on all wires to and from that computer. They can be a culprit.
Good grounding is a must. Everywhere.
Disconnect each connection and inspect for corrosion. Clean and use the clear dielectric stuff from the tube when reconnecting. Every connection you can find.

I am finding connections with corrosion all the time.