Diagnosing your fuel system can be frustrating enough, but turn the irritation level up a few notches if you've been through it from top to bottom and still don't know where the problem lies! If you suspect a fuel pressure regulator isn't holding its own but can't find anything wrong with it, try checking out the vacuum line. A leak can appear in the vacuum port of the FPR (mechanic speak for fuel pressure regulator) and cause it to lose fuel and pressure through the vacuum hose.
An easy way to test for an FPR leak in the vacuum side is to replace the vacuum line going into the FPR with a length of clear tubing. Now you'll be able to see leak as it happens. It will most likely show failure when your vacuum is at its lowest point, as in during acceleration.