Alero Rough Idle?

This is the scenario, I have just replaced the FPR (fuel pressure regulator) since it was leaking and smelling bad. Now that I have replaced the FPR the car idles rough at stops and start up but runs fine when driving. What would cause the rough idle after replacing the FPR? The plugs and wires have not been changed for about 60,000 miles or so and I have no idea when the fuel filter had been changed if ever. When I replaced the FPR, should I have to purge the fuel rail in any way since I released all the pressure or is it something that a code reader could tell me?

Welcome to AF.

It would help to post which engine you have and the year Alero.