mekantor

I'm not sure how widespread this info is, but MB extended the warranty for exhaust value issues on the M157 and M278 motors.

If you have a compression test failure / misfire caused by worn valve seats, at less than 10y and less than 120k miles, you could get a new cylinder head.

I just got my GL550 back from having this done, much better now.

E63SAMG2014

I’ve been told by my dealer they won’t fix it until it triggers a CEL for the exhaust valve recall.

mekantor

Its more common in the SUVs from what I've been told. Do you have the typical misfire symptoms like vibration?

There might be a code stored in the ECU which Xentry can read. IT would say something like "the injector adjustment is beyond acceptable parameters" but it wouldn't necessarily misfire enough to store an OBDII code.