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The late model 1MZ/3MZ no longer use a vacuum referenced FPR and therefore no longer use a FPR VSV (or Fuel Pressure Up VSV).
The 3MZ ECU wants to see constant fuel pressure; 50psi is preferable, but 44-50psi is the accepted range. Cap the vacuum reference on the FPR.
The FPR VSV operates under hot conditions to reduce the likelihood of vapor lock and ease hot starts. It only runs for 2-3 minutes after startup. After that, the FPR resumes using a vacuum reference. Since the newer 1MZ/3MZs run at a constant 50psi, this is no longer an issue, and the ECU can increase/decrease the fuel pulse widths as necessary to compensate.
If you're referring to another engine, I outlined its operation for you.
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1991 Toyota MR2 V6
Ported, rebuilt 3.0L 1MZ
Fully OBDII compliant and California smog legal
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Linear Mode
