The reason I asked is becasue the B-O-P Engineering rear main seal will let oil run out the back of the motor if there's any pressure inside the crank case. The seal is designed to work with higher pressure on the outside of the motor.

You might expect a leaky rear main seal to leave quite a puddle under the car. However, this leak isn't constant. It only leaks when the motor is being driven hard. (Not what you'd usually do in your driveway or garage.) See if you can look up inside the bellhousing for evidence of oil spray from the rear main seal.