If you're pressure is zero in the mornings something other than what we've been discussing is suspect, in my opinion. You could have a bad fuel pressure regulator dumping the excess through the return to the tank. What about clamping off the return after running your car and see if the pressure stays up? That would make first start up way better, the pressure already being in the system. You could have a leaky fuel injector letting the pressure leave out. Try tapping them with a screwdriver handle. It could knock the debris loose that's keeping it from sealing up. Just ideas.