1994 Toyota Camry Car sputters while driving, still picks u

Car is sputtering while driving, still picks up speed, but slowly. It was really cold this morning also. Car was driving fine the day before also. It's runs as if I got my distributor cap wet or something. I recently change my fuel filter in November and my PCV valve. I notice I have an exhaust like before the catalitic converter. I figured I had some bad gas also, so I put some superunleaded fuel with some superconcentrated STP injectercleaner, but all that did was make the car sputter more. Please tell me what I can do. I made a donation also thank you.