1989 Shelby Dakota running real rough

ok so here we go. The truck is pretty much original the best I can tell. I have changed the plugs, wires, cap, rotor,coil, and fuel filter. It seems to get worse the warmer the truck gets. This morning it was running decent just a little rough at lower rpms but smooth once running about 65. This after noon I went to pass another vehicle and the tach quit climbing at about 3000 rpm and it felt like the truck was dieing. I mean it litteraly slows down. I know I am most likely missing something obvious. Any ideas would be helpful.
Thanks Sam

Check your fuel pressure, should be 14.5 or so

Check you codes . Search chrysler tbi key code procedure

Almost certainly a weak pump or weak voltage to pump

Thanks I will give that a try tomorrow.