OK, here's the story. 1988 Dodge pickup, 318. Fuel injection was running rough, too much wasted on it already, so I put on an Offy manifold and AFB. It ran like it had a vacuum leak. Choke it and it smoothed out. Disconnected and plugged all vac lines, no change. Warped manifold? Changed to cast 2bbl. Same thing! Engine has good even compression, roller lifters don't rattle, new dist., cap, wires, plugs, kit in Carter BBD. Idles for 10-15 seconds, then stumbles and loses vacuum and dies. I tried three different AFB's and two 2bbls, one a Holley, and no difference.HELP!