electrical problem i think?

i dont think it has to do with a vaccum leak when i put my hand over the carb i feel good pull and it dies out instantly i have had a vaccum leak and from start to shut off i can hear the problem this one only occurs sometimes my alternator will be charging but suddenly it will wiggle back and forth i can feel and hear a rpm change when it does this man this is a pain in the *** oh and for some reason when the lights are on in neutral it stabilizes then alternator if that makes any sense