Are you using the dash gauge or a calibrated one? perhaps the gauge or the sender unit is faulty.

Also, there are two small O rings at the bottom of the long steel tube that is attached to your oil filter housing lid. I don't believe that the condition of these Orings has a direct effect on oil pressure, but they are often neglected and are rock-hard. You might want to check them out as well-

__________________
Nate Stanley
(Currently Benzless)
1985 F-250 6.9l 170K
2009 SCION XB 36.5K
2003 LS430 78K
2012 Kubota B 2320