At 3:33 he talks about the cam chain tensioner, which I do remember having trouble with on my old CL350.
But what puzzled me, wasn't some internal chain adjustment being talked about in another post about being the cause of some engine noise according to a dealer mechanic, but someone said it was direct drive, so that wasn't possible.
Was that a different chain?
It was in the same post a dealer mechanic called the oil cooler a radiator ;-) but I couldn't find it.