You won't need a vacume pump--your system just needs to be set up with the scavage capacity ratio to pressure pump volume and proper venting/breather balance between the engine and
oil tank--there will be a pressure reduction in the crankcase as the scavage pumps will be pumping
oil/air to the tank which must be vented and the crankcase needs to be vented/balanced to the tank, not to the atmospere
Aviaid makes very good products, they were the leader in the
oil system modifications and everyone else copied them
Jerry