We have the same exact air box.
I pulled mine out of storage to take these photos.
The hose part number is 603 094 07 82.

Your hose is just installed backwards.
Just filp it and you are golden.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

I modified my in/ex manifold from a ca to a non egr fed. I couldnt use the original ribbed hose so i went to homedepot and got a 2" rubber elbow. I had to cut a little bit of the metal elbow underneath the filter housing. Works great!

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

Did you tap the PCV nipple into the rubber elbow and epoxy it into place?

Are you sure that it was 2" and not 2 1/2"? Thanks

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'81 300SD

For now, i just stuck the pvc tube in there. Dont make the hole too big. I bought a grommet to match the tube but i havent asembled it yet. You will need a longer tube. Just bring a measuring tape. The mouth of the rubber elbow is bigger than the body. Turbo inlet is 2.5 in dia.

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

The part # matches what I have, but it's still not a good fit. The hose will fit over both openings, but won't sit flush on the air cleaner, in fact the hose started to crack. Were you using a brand new hose? Assuming that I'm working with a 35 year old hose, I could see how it might have shrunk and become less supple.

In the pic you can see how the hose comes up short.

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'81 300SD