Followup - I could not get a normal (engine off) reading after testing the various two wire combinations and adding a third wire from the sensor for a new ground. (Van's original setup only has 2 wires to the sensor)
Finally got around to checking the voltage on each of the 2 wires. One read 4.9v and the other 11.7v. No wonder the readings on the panel didn't make sense. I swapped out the voltage regulator to a spare one I had on hand, and rechecked the measurements. One read 4.9v and the other 0.4. It appears that a failing regulator had a disproportionate impact on this pressure sensor. I had not noticed anything else odd on the panel.
I then eventually identified which two wires to the sensor and a third to a ground that gave me a reading of only 4psi on the panel. (the wire colors red, green, black from the Dynon supplied plug, didn't seem to correspond correctly) Ran the engine and this seemed to work, with the oil pressure measurements mostly in the 50s & 60s. But, it soon began to jump around a lot and the engine didn't run as smoothly at is should. Jumped out and found spilled fuel around the left carb. Yes, after all this I had a bad float. (the were just replaced in the spring!)
I will fly again some day....