Help with LSD leak

[Dr. Flyview]

Hey guys,

So I purchased a used 3.23 M3 limited slip differential (LSD), put it in the car with some friends. Noticed a small leak. We figured we needed to replace the fill and drain plug washers, so we did, but the leak remains.

Then we figured it might have been overfilled and leaking from the vent. We checked if it was overfilled, and it WAS. However, even after letting it drip out from the fill plug on a level hoist, it continues to leak. Probably about a drop every hour. It SEEMS to be coming from the bottom of the rear diff cover and continues to leak even after the car hasn't been driven for a week. This, to me, means it can't be leaking from the vent, which is higher than the resting level of the fluid? What about the output shaft seals?

1) How likely is it to be coming from the cover?
2) Is there a gasket there? What do I seal it back up with after opening and cleaning?
3) What torque should the cover bolts be torqued to?

Thanks,

Flaviu