what should the fuel pressure be

I thought you would of had more responses by now. Tons of info at other places that are better to deal with your problem. Not trying to be smart guy or anything, just saying. Do be careful though. On my 2001 (5.4) has no return line and what I found online did. So be careful of what year the poster is talking about compared to what you have. (Especially with spark plugs around your year) With mine the problem was a wire not making good connection at fuel regulator. Loosing pressure overnight might be simple as a cracked gasket or loose fitting. I would start with clean filter before I did trouble shooting.