The fluctuation on the brakes is pretty typical. I run an oil accumulator for that very reason. I have ran 3 different pans and have had oil control problems with all 3. I didn't want to have to be concerned if I got on the brakes hard. David is right about the oil running away from the pick up.
You added that you didn't notice it until you lifted getting the car straightened out. Sounds like maybe the oil was moving away from the pick up then. Did you see the pressure drop under power, going straight, at the finish line on another pass?