97 2.7 Tacoma w/ high - low idle (surging) issue fuel pressure FPR

~ added a video link for the surging sound ~
https://linksharing.samsungcloud.com/7xOWLCL8xoJr

Hi folks,

Been searching the forums for a bit, but to no fruitarian.

I have 97 tacoma, 5 spd, 4x4 w/ the 3rz at about 210k miles (coil pack ver).
Been struggling with trying to figure out an idling issue where it goes from 500-1300 rpm constantly. Thought it would be an easy fix when I bought the truck with this issue.

Has not been easy lmao. I've been through and tested the IACV, TB, EGR, PCV, vacuum lines, new FPR, new vacuum modulator, new plugs, upgraded to pink injectors, compression, and a few (alot) more things so far anddddddddddddddddd in short - I plan to take the intake manifold apart next to replace the gaskets (may be a potential vacuum leak culprit, but it did pass the carb cleaner test ) and to scrub the IM clean prior to putting it back on.

Before doing the IM gasket, I hooked up a banjo extension to the fuel rail and did a check for fuel pressure.

Following is my scenario, any thoughts folks? Thanks in advance!

Engine off, key on: 0 PSI (Haynes says should be at 38-46 PSI - other thread searches I saw said this is normal and a mis-print?)

Engine on, idle (with surging in background in all scenerios): constant 43 PSI (spec 31-37)

Engine on, idle, w/ vacuum line removed (removed the PS switch line to IM): constant 43 PSI (spec 38-44)

Engine on, revving: constant 43 PSI

Engine on, idle ~ attached mighty vac tool to FPR's line that connects to intake prior to TB and applied vacuum: Fuel pressure drops steadily as I apply more vacuum. At max vacuum applied, fuel pressure reads 32 PSI ❗

Fuel pressure hold: stayed constant at 43, maybe dropped 1 or 2 PSI after 5 mins.

Is this a scenerio some of you guys dealt with before? what was the culprit? I am dying here lol.