@3Dave Somebody I know very well has been witnessed driving a vehicle around for weeks with a standard fuel pressure gauge duct-taped to the outside of the windshield. He isn't all that swift, but he does get results.
Not to be insulting, but have you checked the fuel filter, and if present - the pickup sock/screen in the fuel tank (if equipped)? It took me two months on a Jeep to find a pink shop rag that somebody stuffed into the fuel tank as vandalism. It would float around and cover the pickup, but only when the fuel level was exactly right along with moon phase. Once the vehicle was shut off, the rag would not be "sucked" to the pickup anymore and it was good for another 2-3 weeks.