If I didn't have a fancy oil pressure gauge, I would have no idea there were any concerns. I put together a motor this winter for my track car (if you are REALLY bored there is a build thread in my signature). The build was done on a tight budget but everything went together and is running fine except for my extremely high oil pressure.
The break in oil is still in - whatever 10-30 was on sale at O'Reiley's - and when cold I'm pegging the 90psi OEM gauge (real gauge from a 1990). Once the oil gets nice and hot, the pressure drops to around 60psi at idle but will go back to 90 when cruising gently ~3k rpm. Anything above that, and it will go back to the peg.
Reading searches for variations on 'High Oil Pressure' on the various forums all suggest a sticking pressure relief valve which certainly sounds likely. It occurs to me though that easily 100,000 miatas with 1.8 BP motors and fake/idiot gauge oil pressure senders will be started today and show 'proper' oil pressure. How many of them have a sticky relief valve and have no idea?
This is a dedicated track car and as such, it will spend most of its life at WOT above 5k rpm. If this valve is really stuck, I could be pushing 150+ psi through the system. If something were to blow on the track the best possible result would be a black flagged session with an oil slick. The most likely result would be that and catastrophic engine damage. The result I fear most is all of the above plus 4 quarts of oil hitting the outside rear wheel at 1.3g right after I pin the throttle hitting an apex causing me to take out myself and 2 other cars. Bent metal and injuries or worse.
I'm going to try a few simple things to troubleshoot my car before I go through the PITA of pulling the engine and putting in a new pump. First, I'm going to put a new filter on just for grins. Next, there will be a gentle tap with a hammer on the oil pump case while it is running. Don't get excited - I'm not suggesting winding up with a 10# sledge. Lastly, I have another OP sender that I will install just to make sure I get the same behavior.
This pump might be fine if I unstick the valve but considering my time is around 2 full days to R&R the motor and oil pump (working on jackstands in my 2 car garage by myself, pan and whole front comes off, etc…), I'm just going to put a new pump in to minimize the chances this will need to happen again.
One way or the other, I'm going to get the oil flowing properly through this engine before I take it to the track but I do wonder how may cars out there have this exact problem and never know it because they just have the idiot light gauge. Ignorance is bliss...