Car stalled out and check engine light came on and 2 codes, P0171 and P1171

both mean lean. unfortunately there are a ton of reasons to be lean. any air leak, pump shutting off vacuum leak. if you have a scanner watch the maf values. check/clean the maf.

A code P0171 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty
Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor
Possible cracked vacuum or PCV line/connection
Faulty or stuck open PCV valve
Failed or faulty oxygen sensor (bank 1, sensor 1)
Sticking/plugged or failed fuel injector
Low fuel pressure (possible plugged/dirty fuel filter!)
Exhaust leak between engine and first oxygen sensor

That could also bring us back to a faulty fuel pump, which is I where I started with my first response to your thread.

normally the pump will not cause the engine to die like a switch, and takes a while for the pressure to build to refire

Dave,
does the car also have Camshaft position sensor? if it does, have u replaced that one, or its reluctor (magnet pickup thing). I had 92 Bonneville SSEi, it would run normal, drive u to places but then once in a while would stall as well. It had a bad reluctor magnet. infact its magnet was crumpled and there was only left overs left holding on to each others, it didnt stall after i replaced that magnet, (which was a bitch to get to lol, and i end up replacing lots of other crap on way to it just for hell of it)

The camshaft position sensor was replaced and the stalling issues became more frequent so we re-installed the old one.

I want to test fuel pressure but don't see a fitting on the fuel rail to do it. Where is the fitting located to do the fuel pressure test?