I have a 65 289. I purchased this last august and it ran beautifully for the rest of the season. I stored it with a full tank of ethanol free gas and stabil. Since I took it out of storage, i have been having an issue. It will drive along fine for 30 -40 minutes and then while driving it will suddenly lose power for a few seconds and then run fine again. This sometimes happen 2 or 3 times in a short span and then run good again. I replaced the fuel filter, and someone suggested an additive to clean the carb. Any help is welcomed