Those pressures were actually taken from a downloadable Isuzu Workshop/Repair Manual, not a users/owners manual.

2000 Isuzu Workshop Manual

And from this thread; http://www.vehicross.info/forums/showthread.php?t=20985

Quote Originally Posted by Y33TREKker View Post
My initial search term was "fuel pressure", and when following one of the "fuel pressure regulator" search results, I saw a link that said "fuel system diagnosis". After that I used "fuel system diagnosis" as my search term, and the fuel pressure readings were listed under a few different topics.

Most of the results were in section 6E - Engine\ 6VE1 3.5L Engine Driveability and Emissions.