Help!! My 79 450 starts but die
 

Sure could use some help here. My 79 450 will start but idles high for a couple minute then dies down and sputters and dies. Will start right back up but does it again. Can not give it any throttle at all. It dies the second you try to accelerate. Push it to the floor and it backfires and misses, let off the throttle and it revs up and then dies . any ideas. Lance