Sprinter went in again for warranty service of the EGR valve.
They did a replacement of the valve and a full cleaning of the chamber that comes after the valve.
I have to say that Nathan at MB Westminster has been a pleasure to work with.
They loaned me a GLK for a couple of days during the service (very nice SUV)... the only problem therein is that now my wife wants one
The rust on the back doors of the van is progressing rapidly
I've put in a request with Mercedes Benz for consideration on fixing this issue as a defect. The "rust warranty" expired in March - but obviously the issue has been getting worse and worse for the past 30,000 miles.
I'm still waiting to hear back on their decision.