89 F150 302 EFI
i would really check the fuel pressure regulator. it sounds just like a problem my buddy had on that exact same truck. he replaced all the crud you've replaced before he finally figured it out.
1990 F150 Custom 2wd
300 straight-six, Mazda 5 speed
1971 F100 2wd
360 FE, C6
"It doesn't break 'til I fix it"