2001 9-5 Start then die
 

Hi,
I have a 2001 95 that I am trying to get going for my granddaughter. It had a bad fuel pump, replaced it and cleaned out the tank. It started up once the lines were purged, and ran great for about 10-15 minutes. Now, it will start fine, then almost immediately dies.If I "Pat" the accelerator, it will keep running, no misses.
The moment I quit patting the accelerator, down it goes. I have tried to check the rail pressure, as near as I can tell it starts at around 50 psi, and as I "pat" the accelerator, it drops to around 40, back up to 50 etc. The only OBDII scanner I have that will work on it is a very old and mostly useless unit, and cannot give me
much info. Newer unit does not recognize it, even when I go to manual and choose 1941(?) connection protocol. Right now I am leaning towards the fuel pressure regulator, it is responding to the engine vacuum, however the car sure acts like the fuel supply is being cut off.
Any ideas would be appreciated.