Fuel Pressure Regulator
WARNING: This page is about a different car, the 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
The fuel pressure regulator (2) is contained in the fuel sender assembly. The fuel pressure regulator is a diaphragm relief valve. The diaphragm has fuel pressure on one side and regulator spring pressure on the other side. A software bias compensates the injector on-time because the fuel pressure regulator is not referenced to the manifold vacuum. The fuel pressure regulator keeps fuel available to the injectors at a regulated pressure.