Most N/A engines have a fuel pressure regulator complete with vacuum line. Your engine should have one. Normally these regulators only lower the pressure when the vacuum increases (pressure inside the manifold drops).
If the standard regulator can also raise the pressure under boost? You would have to test that. But you do need one that both lowers and raises the nominal fuel pressure based on the pressure in the inlet manifold. That's after the throttle and you should have that connection already.