Dakota V8 overheating and stalling. Starts right up after day or two. Help?

Hi, I have a 1994 Dodge Dakota V8. It only has 80,000 miles on it. It sat for awhile which is why the low miles. I've been having this problem. When I drive for any distance (25+ miles) it will start running rough. Sometimes it overheats, sometimes not. It will act like it isn't getting enough gas. It will sputter and slow down and the rpms jump all over the place. Sometimes I can tap the gas and it will run for a little longer but usually it just backfires and stalls. If I leave it for a day or two it will start right back up. Here is what I've done so far:

tested battery
changed wires & plugs
changed air filter
checked fuel pump
put on new coil
the thermostat is only a few months old
added dry gas
cleaned maf
cleaned throttle body
changed pcv valve (it was broken)

I have a scanner coming the mail and I'll put that on but I'm at a loss. This is my work truck and I could really use some help. Thanks for any ideas!