It doesn't look like a PO hack job.
Near the airbox on my sdl I see what looks like a primary fuel filter w/ no fluids in it.
What's it for?

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82 300D....went to MB heaven
90 350 SDL....excercising con rods

It's a filter/particle trap for one of the lines. Maybe the vent that goes to the cabin.

Sixto
... stay tuned