2000 S40 fuel delivery problem

I was driving last night and all the sudden the car started cutting out. Whenever I would give it gas the rpms would drop. It seems like the car went into limp mode. I had to stop at a red light and the car died. Luckily it started back up and I was able to limp it home which was only about a half mile away. I took off the throttle body and gave it a good cleaning this morning. Also cleaned the TPS and the IAC. I then replaced the fuel filter. Put it all back together and the car will barely start, but if I give it enough gas right when started it will run at high rpm fine for about 5-10 seconds then the rpms drop and cannot get them back up and the car eventually dies. Sometimes it will start up and seem to idle normal but when I touch the throttle it starts bogging and eventually dies. Checked the fuel pressure and it is at 8 when the ignition is on and at 10 when the car is running which seems to be really low. The car has had a rough idle since I bought it about a month ago and has always kind of lagged off idle. It seems like a definite fuel problem, but would it be a fuel pump or the fuel pressure regulator? Has anyone had a FPR go out and if so what are the symptoms before it goes?