I have a 2002 3800. The car is rough at idle at times. While driving, the car starts missing and sometimes dies. When main vacuum line is disconnected from the fuel pressure regulator, the problem with the rough idle goes away. I'm considering plugging the vacuum line and driving down the street to see if it corrects that problem also.
Does anyone know what I'm dealing with here?

 

After having the mass air sensor replaced runs like new. Thanks Yellowmonte