Fuel Pressure Regulator
WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
Fuel pressure regulator is a diaphragm-operated relief valve with injector pressure on one side and manifold pressure (vacuum) on the other. Pressure regulator maintains a pressure of 55-62 psi (379-427 kPa) under all operating conditions. Pressure regulator compensates for engine load by increasing fuel pressure when low manifold vacuum is experienced.