87 tbi 350, engine stalls

[bbchevy]

I've replaced the fuel filter, cap, rotor, plugs, wires, coil, and changed the throttle body to one off another running truck. And i havent found any vacuum leaks. but still the truck insists on running perfect for 5 seconds then stalling out. if you give it a little gas it will stay on longer, but has no throttle response at all. bogs right out when you try to rev it. and it just gets worse when it warms up a little bit (if you can even keep it on that long). I have no idea about what the problem is.