what's the temp of the oil after a hard run?
If it's getting too hot, it will cause lower pressure readings.
is there enough oil? maybe too much?
If there's too much oil, the crank will cause the oil to foam up which causes the pressure to go down.
If there's not enough, the oil may not be returning to the pan fast enough.
The other thing is, doies it have the right pick-up installed for the pan? Could also be the pick-up screen fell off.