I have a cam with similar numbers as the 224/230, but with a little more lift and duration. On the stock cam, I ran the fuel pressure at 39-39 wide open throttle ie, no vaccum. Is this still ok for the new cam, or do I need more fuel now?

 

well at idle you'll autmatically get higher fuel pressure because of the vacume loss with the cam causing your FPR to go richer.

 

I've always been told to run what ever pressure the injectors are rated for. If you've got 30lb injectors they will only flow 30lb if the pressure is set for what the manufacture says it should be to flow 30lb. I run mine at 42psi.

 

No.

The vacuum compensation on the fuel pressure regulator is intended to control the DIFFERENTIAL pressure, not the rail pressure. Your gauge only reads the rail pressure, and that is not the only thing that detemines flow capacity of the injectors. The "pressure" at which the injectors are rated is the DIFFERNCE between the rail pressure and the intake manifold pressure (MAP), when measured on an "absolute" scale.... so... if your rail pressure (what you see on the gauge) rises because there is less intake manifold vacuum (higher MAP), the DIFFERENTIAL pressure between the rail and the intake is held constant, and the flow through the injectors stays constant.... it does not "go richer" because you gauge sees that the rail pressure is higher.

A common misunderstanding.