Engine Runs Rough and Stalls

4.3L Engine, Auto-Trans. Engine starts fine and idles good @ 600RPM. When I put it in Drive, it starts running rough and stalls out. Also I seem to get a humming feedback noise thru the radio. This problem is intermitently. I don’t get the feedback thru the radio at the time when it is running smooth. Any help on this problem would be appreciated. Thanks.