Starts, runs for about 3 seconds, and dies
 

So I just bought a 92 Dodge Dakota V6 auto that didn't run. When I first bought it, it would barely start but after some new spark plugs now it'll start, run for approximately 3 seconds and die out. If I repeatedly tap the accelerator or get it just right and barely touch the accelerator I can get it to run indefinitely, however still rough. If I hit the accelerator any harder it just falls flat. I've checked timing and fuel pressure and they are both great. I've changed coil, spark plugs, cap and rotor, little ignition sensor on distributor, tps, map, iac, fuel filter, cut the muffler off to make sure it wasn't rusted up and there is no cat to be plugged up. I'm probably forgetting something else as well. Any ideas that could cause this problem? Btw most of the parts have either been pulled off my daily 96 v6 5 spd or my running parts truck 93 or 95 (can't remember which) v6 auto so not much money has been thrown into it. Any ideas of what it could be?

make sure the tps isn't backward. last guy might have "fixed" it before.