Just to add some petrol to the fire, when I went into the Mercedes dealer to order the gaskets and seals needed to do this job I was told by the friendly parts person that it comes as a kit. I asked him if he could order me one and he told me they kept them in stock as ''he sells so many''
He also recommended a pipe joiner that I would probably need that didnt come in the kit. He also had that on the shelf. When I stripped it the pipe that joins the two parts of the manifold was indeed need of replacement as it was a light alloy and badly corroded.
He also had an inlet manifold in stock but said '' there are better options''.