Haunted carb

I have a 78 L82 auto trans that ran great untill last weekend. I noticed at idle the rpms would jump up about 300 rpms once or twice a minute, lasts a few seconds and then returns to normal. It would do this randomly. I didn't think it was timing, I rebuit the distributor 3 months ago and it ran great. Had to be the carb, it had never been rebuilt. I pulled it off and brought it to a reputable carb guy to rebuild. Got it back put it on. Now it revs up all by itself,(darn thing is haunted), goes from 800 rpm to 2000 rpm and back down. Gets up to 2000 rpm the auto choke closes, rpms go down to 800 the choke opens and begins again. I have held the choke open and it just quits. Ihe pluged all the vacume ports including the vacume advance and it makes little difference. I can't find any vacume leaks. What am I over looking? Thanks for any sugestions