For the past 10 months since I bought this 260,000km 945T, I have been trying to stem the oil leaks. The very first thing I did when I brought it home last February was to pull all the oil breather lines and ensure they were clear. I also removed the oil box and sprayed copious amounts (a full can)of carb cleaner into it to ensure that it was not plugged. I got lots of junk out of it. I did lots of other things as well, but the long and short of it was that I still had oil leaks.
Today I pulled the oil box off the side of the engine again. This time I installed a shiny new box in its place. Then I decided to hacksaw apart the old one, seeing as it weighed considerably more than the new one. I also wanted to see exactly how this magic box works. What I found was that the small opening (smaller than I would have thought) in the interior that permits the crankcase fumes to enter the larger precipitating part of the box was completely plugged with crystaline carbon crud. And I mean plugged!
I beleive this was the cause of my problem of oil leaks, and am writing this to encourage people not to assume that it is always possible to properly clean a fouled oil box. Replacement is the answer.
John D