If there is less than specified fuel pressure, and you know your fuel pump is new and not an option, you can continue from there:
Check the fuel lines for leaks. Pressure leaks will be evident. Check for vacuum leaks in the fuel system (anywhere pre-pump), crushed/blocked fuel lines, and a plugged fuel pump sock/screen. Replace the fuel filter, then try your fuel pressure regulator. Very rarely does a fuel injector limit fuel pressure unless it's stuck open, but then you will be able to notice excessive unburnt fuel in the exhaust, especially since it will start and run.