It so happens that my neighbor who owns a BMW repair shop probably has the answer to my problem. Even his wife noticed how rough my car ran, they can't help but hear me leave the house.
He does not believe that my sudden rough running has anything to do with the octane booster but that most likely I picked up water during the last fill-up. He said that since premium is not sold as much as regular, water condensation can build up in the gas station tanks once the temperature starts dropping. He is running back to the shop to get some dry gas that will break up the water molecules. I will post the precise name of this stuff once I get it and the results.