I know this thread is a month old, but did you ever figure out what the problem was? I'm curious because I've been experiencing the same problem with fp's not building. I originally thought it may have been my fuel pump dying a slow death. Turned out to be fine. So I've replaced the fuel filter just today (80,000 and my first filter replacement ). Although it appears that the car drives/sounds smoother, pressure isn't building as fast as it should.

A