Mopar 360 idling strange

It's starting to get very cold at night up here in New York and as of this passed weekend my car has not been likening it at all, usually it will start second crank and hold idle but now it just does if you don't give it gas, then as soon as it's idling it sits around 500 it drives fine it's just idling very rough, it has all new gaskets for the carb and intake manifold, if I give it a little gas at idle it'll bounce up to 1000 hold for a little then slowly make its way back down to 5 like I said it just started doing this and the car ran strong and fine the day before