good gah.

READ THE FSM.

43.5 psi, or 3 bar referenced to intake manifold pressure.

that means that if intake manifold pressure is -15inHg (-7.5psig), then you should see 36psig. conversely, if boost pressure is +7.5psig, then you should see 51psig on the gauge.

it is references to intake manifold pressure because injector flowrate is dependent on the difference in pressure between the two sides of the injector (fuel rail on one side, intake manifold pressure on the other). in order to maintain constant flowrate for a given pulse width, the fuel rail press must increase with manifold press

also, read up on psig/psia.