[robinaube]

If your sump cover plate is flat, then the problem may be the case itself. If you want to install a deep sump then fine do so but that won't solve the problem if the case is warped.

I suggest taking the sump plate off again, cleaning the area completely. Check the case for flatness. Double check the sump plate for flatness. Install the sump plate with a new gasket. Tighted the sump bolts with a torque wrench. Then start the engine. If you find anything is not flat, then replace it. If you find that the case is warped, then you are looking at a rebuild.