I believe you are referring to Job AR15.12-P-2003GQ, "Remove/install ignition coils". It does not call for removing the "bulkhead" on the W166. However, Step 3 is to "Remove intake manifold". That is where it gets ugly. Job AR09.20-P-1961GQ, "Remove/install intake manifold" Step 6 is to "Remove bulkhead (78)".

There are 2 bolts at the rear of the intake manifold that must come out. I cannot see any way to remove those bolts with the "bulkhead" in place. Believe me, I've tried.

I am very familiar with the links and posts over at MBWorld. Post #14 by JohnnyC with the photo of the manifold removed...is on a GLK. Post #13 by NickW has a link to a procedure for changing the plugs without removing the manifold....on an SLK. The ML is different due to placement of the engine very far aft in the engine compartment and other interferences to the sides. Regardless, unless someone posts a reasonable means to remove the "Bulkhead" I am going to try to non-removal approach.