i just bought installed a new intake manifold and put everything back together. I dont think i have left anything or fergotten anything. It turns over and begins to idle, then there is a bang and smoke exits from the carb. its a grey smoke. I dont know how to describe it other than a back fire. The truck then shuts off. Just incase you need to know its a stock 350 with verylittle modifications on it. Any ideas guys????