What does a fuel pressure regulator do?
The role of the fuel pressure regulator is as the name implies: it regulates the pressure of the fuel entering the fuel injectors.
On older vehicles that use a continuous fuel system, the regulator is usually a vacuum control unit mounted on the return side of the fuel rail. The regulator sends excess fuel back to the tank to maintain fuel pressure. A vacuum line connects the regulator to the engine vacuum source, allowing the regulator to vary fuel pressure based on engine load.

One other thing to note.
How do you know if your fuel pressure regulator is bad?
1. Engine stall / poor acceleration
2. black smoke from exhaust pipe
3. Spark plugs appear black
4. Reduce fuel mileage
5. gasoline in vacuum hose
6. engine backfire
7. The engine won't turn
8. Fuel pump is too noisy
9. Fuel dripping out of the exhaust