Fuel Pressure Regulator Assembly
WARNING: This page is about a different car, the 2004 Chevrolet Monte Carlo and 2004 Chevrolet Impala. 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 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.