Fuel Pressure Regulator
WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 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 mounted at the end of the fuel rail. See Fig 1 . 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 fuel injectors at all times. The pressure regulator compensates for engine load by increasing fuel pressure as the engine vacuum drops.