2003 workhorse P32 fuel pressure

I think it is 56-62 psi, but either way yours is low, I added a fuel pressure gauge to mine as one of the potential disaster failure modes on these engines is low fuel pressure as the ECM assumes you have correct fuel pressure for its fuel injection timing, as there is no fuel pressure sensor, low fuel pressure can therefore cause the engine to go lean and all the bad things that go with it (burned pistons, detonation, etc.) The fuel pressure regulator may be adjustable depending on the year, mine requires a security torx bit (torx screw with a center post) to adjust, though you should first check it by removing the vacuum line from the pressure regulator and see if fuel pressure goes up to the normal range, just be careful as a failed fuel pressure regulator may allow fuel to squirt out the vacuum line.

p.s. confirm with a mechanical fuel gauge, as a bad sensor or even a poor ground can through off the reading on the electronic dash gauge.