Fuel Pressure Regulator Assembly
WARNING: This page is about a different car, the 2004 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
The fuel pressure regulator is a diaphragm relief valve. The diaphragm has fuel pump pressure on one side and regulator spring pressure and intake manifold vacuum on the other side. The fuel pressure regulator maintains a constant pressure differential across the injectors at all times.