93 Camry 5s-fe problem

Hello, recently i've had a problem with my 93 camry. I had a mechanical oil pressure gauge installed and was monitoring my oil pressure when I first started my vehicle. It started up, shot up to 80PSI. Every time i'de slightly touch the throttle, it would jump up to 100 (I am assuming it goes over 100Psi because its only a 100Psi oil gauge and it was pegged out). I shut the car down immediately. I waited a minute, re-started it and it was at 75Psi. I tapped the throttle again and this time it jumped up, then went down to 2Psi . my oil pressure light turned on at this time. I pulled the pan to inspect the Main and Rod bearings and they feel tight to the touch (No abnormal sounds). I removed the pressure relief Valve on the oil pump, and noticed the plunger was stuck at the top of the cylinder. The inside of the cylinder was a brown varnished looking color. I tried to remove the plunger valve, but I couldn't get it to drop out. I cleaned the brown varnish out so it was silver again, and re-installed the spring. I re-installed the oil pan and started it up. Same thing. Stuck at 2Psi. once Warm, if I give it gas to 3000 RPM, it goes to 25-30PSi. The throttle goes in sync with the oil pressure gauge. If it Rev it from 2000 to 3000, the needle goes along with the RPM. I know that as the motor increases in RPM, the oil pressure gauge will increase too, this doesn't rise the same as it used to. Its instantaneous with the Throttle. From what I've read, a relief valve stuck all the way up will cause very high oil pressure. Is it possible that the relief valve could have been stuck all the way up for some reason, then when the RPM spiked to 100+ PSi, it partially opened the valve making it stick partially open all the time not allowing any pressure to move?

The motor does not have any sludge. When I first put the motor in (Bought the vehicle with a spun bearing) it had a minor sludge issue. None in the oil pan, but a very little in the valve cover. I did oil changes every 1000 miles to resolve this issue.

I did not remove the bearings and check the clearances with plastigage yet, because this is my last resort.

Do Bearings really just all of a sudden loose oil pressure? I thought that bearings would gradually wear out, causing the pressure to gradually go down little by little until they need replaced.

Also, if you simply would like to replace engine bearings if there is not a huge oil pressure problem.. instead of running plastigage, can you install Standard bearings and be OK? Or does the crank wear out with the bearings, leading to having to resurface the crankshaft?

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The motor I installed had 102,000 miles on the odometer. I've put about 10,000 miles on it since the install.

Done the following in the 10,000 miles:

Transmission filter
Transmission shift solenoids / Valve body
Distributor Cap, rotor, Coil, Pickup
Igniter
Spark Plugs, wires
IACV
EGR
TPS
VSV
All Vacuum lines
Throttle Body cleaning
Alternator
Timing Belt
Timing tensioner
Timing idler pulley
Oil pump gasket and O-Ring
Water Pump
Flushed radiator
Numerous oil changes
Brakes All around
Rear Main Seal
Differential Drain / Refill
Axles (both sides)
Struts
Strut tower bushings
Control Arm Bushings
Sway bar bushings
Brake fluid change
rear Wheel bearings
Front wheel bearings
inner/outer tie rods
Rebuilt P/S pump
Rebuilt P/S Rack
Valve cover Gasket
Spark Plug Tubes
Oil Pan Gasket
Coolant Bypass O-Rings

theres more but I cannot think of anything.

If you guys have any incite onto my low oil pressure problem, i would greatly appreciate it. I've posted some questions on an online forum for toyotas, but they aren't that knowledgeable when it comes to oil pressure issues. I've read on a seach that No oil pressure indicates bad oil pump, low oil pressure indicates bad bearings. I am hoping that the bearings are not bad, but like I said this happened in such a quick amount of time that I find it hard to believe the bearings just "went bad".

Thanks again!