You know...that's very helpful! I think a weak battery can cause all kinds of problems. Seems like my problem went away for quite awhile after I changed the battery over a year ago. A little extra voltage makes all the relays perform more consistently. It is hot as hell here in Houston 99 degrees this time of year and that drags on the battery.

I threw a fuel pump at it because it made sense and it was only $78. Obviously I didn't buy the whole assembly for $364. An extra 15 minutes of simple modification is all it takes to install a universal higher flow unit.

I'll check the vacuum line to the fuel pressure regulator but that actually reduces fuel pressure at idle so I don't think it would cause this particular issue. I already replaced the fuel filter/regulator just because it was cheap and had never been changed.