Im not aware of any system that regulates the vacuum. Now its possible that you have a vacuum leak but I would have expected that to show up, at least in part, with your fuel pressure test, that is to say fuel pressure readings would have been off.
So we know it starts, we know it started after your replaced the fuel pressure regulator. The first thing to do would be to start tracing out those vacuum lines and make sure they are all in good shape (no cracks, holes, etc) and are all connected.
You kinda got me thinkin' you have a dual issue. Try and start it up this morning and let it run if it will start up. If it still just cranks and no start, post up here and let us know. I'll try and keep an eye on the thread, but I'll be at work so I cannot promise anything.
