As in, reading rich = less pressure

lean= more pressure


?

Need an adjustable fuel pressure regulator.

https://www.thirdgen.org/newdesign/tech/o2tuning.shtml

Not if you're still running the ECM controlled factory fuel setup. You won't be able to with an AFPR either. The O2 sensor will have that gauge swinging back and forth between rich and lean constantly (just like it's supposed to).....

I mean, use the A/F gauge as the measuring tool for seeing the car be lean or rich, need more or less fuel, and then making the needed pressure adjustments at the after market adjustable fuel pressure regulator?

I thought that's what you meant, but if the computer is in Closed Loop it will constantly be shifting back and forth between rich and lean. That's what it's supposed to do. If you unplug the oxygen sensor, you might get an little better idea but the car will probably run like old dried donkey dung and also set a check engine light/code.....