Olds has been starting rough the last few days. Set a code p0171 a few weeks ago and found a few vacuum leaks. Found some bad/loose vacuum connections. Checked fuel pressure and it was 32-34 while running. Key off and it was at 40. When I restarted engine stumbled and pressure was at 20 then it would slowly come up to 32 again. Restarted again and it would die. I took it to work and it almost stalled again and I revved it up and drove on the highway no problem. I am hoping against a fuel pump because of the expense. The fuel filter was changed last fall and again a few weeks ago. I have been getting about 24 mpg on the highway and once in a while 26 mpg. Any help would be appreciated.

If the fuel pressure is 40 engine off, but almost 10 lbs less running, I'd see about replacing the fuel pressure regulator and then retesting.

When you check fuel pressure (key off) and it reads 40, does it drop off? Pull the vacuum hose off the fuel pressure regulator (key off) and smell for gasoline in the hose. Both of these are signs of a failed fuel pressure regulator.

I will check it this morning I have a spare fuel rail with a pressure regulator.

I didn't get the regulator change because I found a small leak on the fuel line that connects to the fuel rail on the backside of the engine. I replace the white plastic connectors on both the supply and return lines. My pressure is still at about 35 while running and it died on me once after I started it. The pressure drops down to about 20 or so and then dies. I restarted and it went back up to 35 and ran fine.