I replaced my breather box today as part of a major maintenance I did.

I found that the old one had ruptured along the seam where the top and bottom fit. I have some pictures I can post later.
If you're looking for an oil leak, take a look at the seam on your breather box.

and if you're in california, the EGR system is mounted on a bracket, which is held down with the same bolts that hold on the breather box. It makes the job about 20 minutes longer and requires box-end wrenches bigger than 19mm. (I think 21 and 22). I used vice grips because I've had my egr apart once before.

don't forget to NOT remove the plastic tube that extends into the block. It's part of the oil pump. Nasty to fix if you pull it out.

Happy Bricking! :D
-Will
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1990 740 Turbo, on its way to stock specs, maybe beyond