I agree with Olddog. The gauge pressure port on my adapter plate is on the return side of the plate, after the
oil has passed through the filters and cooler. I would first verify the gauge is reading properly, then I would remove one hose from the filter and loop it back to the adapter plate to bypass the filters and see if that makes a difference. The
oil won't be filtered, but would probably be safe as a test for a few minutes. Are the pressures your quoting with the
oil cold or hot?
Brad W.