I have a 78' Dodge B300 Maxi with a 400, 2 barrel. It had sat quite a while when I had bought it, we replaced wires, plugs, dist cap, fuel filter, drained gas out of tank. Would run and drive would get up to 40 or so and then backfire and die. So bought a remanufactured carb and installed a new manual choke thermostat, it has been timed, now what it does is it will start and run maybe 10 to 15 seconds and then die, you can give it gas and it will stay running but when it idles down it dies. So I don't know what to look at, I was told the intake manifold had a lot of carbon built up? We have seafoamed the engine and run some through the gas tank with the old carb, it looks as if it gets gas when you open up the choke and press the accelerator down, it shoots gas. Don't know what it could be, fuel pump, coil, egr, ballast resistor. Any help or ideas would be greatly appreciated.