Ive been trying to figure out why Im seeing a pressure drop on my fuel pressure sensor (912is) when I start the engine. I see a full 43-44 psi before start and when running consistently ~38 psi (either fuel pump). Im wondering if it could be due to the fuel pressure regulator trying to hold constant pressure relative to the manifold pressure. I.e. when I start the engine manifold pressure drops so the regulator also drops the pressure slightly and my gauge shows the drop. For you 912is guys does that make sense? Its just a hypothesis. What are yall seeing before engine start and while running? Im using the 70 psi UMA fuel pressure sensor right before the fine filter.

Thanks as always!