Engine Oil Pressure

so to clarify all of your readings are from the OE gauge?
15 dollars will get you a cheap mech oil pressure gauge at your parts house. install that and see what your pressure is. I would say anything over 24psi hot is good.

A spacer will not affect the oil. A breather air plug will not affect the liquid oil pressure significantly. Switching valve cover style can be the cause of fitment issues, but not oil pressure. Get a T fitting if you lost it, fix the line or get a new electrical gauge. The factory one could even have a bad connection at the sensor to cause these boumcing symptoms. But yes, a new pump can go bad, so can a new bearing. Bouncing pressure is odd unless there is a low oil level in the pan.

Light weight oil will make it bounce also along with a lower psi reading, it did in mine. When I have 10w-30 synthetic in it drops lower when hot and bounces more. When I switched back to 20w-50 synthetic it raised it solidly even when hot.

Being your filter is on the left, turning left would cause whats inside to move right. Bad filter?? Or it and or sending unit has a leak maybe??

You need a good mechanical gauge. All that everyone is doing is guessing here. Hard facts will solve your problem, if you want some outlandish guess from me let me know and I'll think of a really good one.

Little green men in the oil pan that are taking turns blocking the sump just to tick you off is my wild guess.

Congrats! I like cheap fixes! I'd still check out the factory sender and wiring. A new sender should be cheap too. @jrichker has a write up on a restrictor for mechanical lines that looks wise. If the line breaks behind the dash, what a mess, and if it breaks under the hood and spurts on the exhaust, that's just scary.

Mechanical oil pressure gauge installation..
1.) Remove old pressure sender. It is located down by the oil filter and has 1 wire on a push on screw connector.
2.) Install ¼” pipe tee fitting with a short ¼” nipple on the place where you removed the oil pressure sender.
3.) Install the original oil pressure sender back in one of the tee ports.
4.) Install the gauge line restrictor in the remaining port of the tee.
5.) Connect the hydraulic hose to the gauge restrictor. Be sure to route the tubing or hose away from the exhaust manifolds. Be sure to either use hydraulic hose for the pressure line. Do not use copper tubing for the connection to the gauge restrictor or engine. Over a period of time, the vibration will work harden the tubing and cause it to crack and fail.
6.) If the gauge is going to mount under the hood, connect it to the end of the hose or flex tubing. Use some Tie-wraps to secure the gauge and its plumbing to the wiring harness on the driver’s side inner fender.
7.) If the gauge is going to mount in the passenger compartment you get to find a place to run the tubing through the firewall. I suggest that you pick your spot from the inside since that is the area with the most difficult access. Do not run the tubing through the exact same hole as the steering shaft. It will tangle up with the steering shaft and cause major problems.
8.) Install the gauge inside the car in the location of your choosing. Connect the pressure line to the gauge and secure it out of the way of moving parts with Tie-wraps.
9.) Be sure to ground the gauge lighting wire to clean, shiny bare metal. Connect the other wire from the gauge lighting to a light blue/red wire on the radio wiring harness. There are 2 connectors in the radio wiring harness, but only one of them has the light blue/red wire you need for gauge illumination. Solder the gauge lighting wire to the light blue/red wire on the radio harness and cover the soldered joint with heat shrink.

How to solder like a pro - Ford Fuel Injection » How To Solder Like a Pro a must read for any automotive wiring job.

Be sure to use a gauge restrictor fitting in the pressure line going to the gauge. The restrictor will prevent all of the engine's oil supply from ending up on the pavement before you can stop it if the gauge line fails. I had a gauge line rupture, and the restrictor fitting saved my engine from serious damage.