My 140 series has one of these and from what I can tell it is a vacuum filter going to atmosphere. If needed I can post a photo of my emissions sticker under the hood. It has a drawing of it with all the vacuum lines.

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1995 S-350
370K + SOLD
1952 220B Cabriolet
39K kilometers + SOLD
1998 E300D
310K +
2012 E350 BlueTec
120K