Has the weather changed? Holly carbs are real prone to idle change in damp weather. My old 390 has a holly and it needs a little help when we get weather changes but runs like a top the rest of the time, all of the ones I have owned were kicked by that mule. Many years selling parts and working on holly carbs introduced me to a saying, if you don't like the way your holly runs today wait a day or two it will change. And there is some truth to it, they have alot of small passages compared to a craker box autolite and are prone to dirt, very prone. Follow the good advice above if it don't clear up, oh and buy a filter and get it inline or face this problem many more times. Good luck.