* Controlling fuel pressure: The regulator is a valve that adjusts the amount of fuel pressure that's allowed to enter the fuel rail. It does this by either venting excess fuel back to the fuel tank (returnless system) or by controlling the amount of fuel flowing from the fuel pump to the fuel rail (return system). A 1991 Corvette likely has a return system.
* Maintaining consistent fuel delivery: A constant fuel pressure is crucial for proper fuel metering by the fuel injectors. If the pressure fluctuates, the injectors won't deliver the correct amount of fuel, leading to poor engine performance, rough running, and potentially damage.
* Responding to engine vacuum: Many fuel pressure regulators use engine vacuum to adjust fuel pressure. Higher engine vacuum (at lower throttle openings) results in slightly lower fuel pressure, which contributes to good fuel economy and cold-start operation.
In short, the fuel pressure regulator ensures that the engine always receives the precisely controlled amount of fuel needed to run smoothly and efficiently, under various operating conditions. A malfunctioning regulator can lead to a variety of drivability problems.
