... our stock unit is already a Rising Rate FPR, with a static base pressure of 43.5psi correct?

you bring up a good question. i never monitored the stock fuel pressure. lets look at this from an aftermarket perspective. yes you feed a vacuum line to the FPR. that tells me that when you are idling and there is vacuum in the manifold. it actually lowers the fuel pressure, but then as you throttle up the pressure rises.

That being said, lets say you add some boost to the system, will the stock FPR continue to raise the fuel pressure like an aftermarket one? and what is the rate that it does raise the pressure. 1:1? multiplier? I just dont know.

the stock FPR in the 3S-GTE looks very similar to the one in the 5S-FE and i believe it is a 1:1 rising rate. Im going to guess that the 5S-FE regulator is a rising type but is limited to what it can do. Meaning once it reached a certain pressure, it wont raise it any more.

Yeah that's what I was thinking. The 2JZ-GTE is supposedly a rising rate as well.

I wonder how much our stock one goes up to if anything...

i think its safe that any factory turbo Toyota is rising

I have my suspicion that the 2JZ regulator fits in the 5S rail. You think you could verify that Smaay?

If it looks like it will fit, it probably will. Toyota use metric fittings across the fuel system, you shouldn't run into any crossthreading issues with imperial/sae mismatching.

i havent had the stock rail on my supra for years. sorry i cant confirm this. try supraforums and MR2oc.com they might know.

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Yeah that's what I was thinking. Will probably buy one to try it out.

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That sucks, thanks anyway.