I'm sure others will have some good suggestions; but I would first inspect your plugs and wires, see if they are good, see if they have oil or have been running hot. Also, your knock sensor, I would pull it and inspect for cracks, make sure to torque to spec when re-installing. Also, if you haven't done so yet, since you reconnected the O2 Sensor, you might try disconnecting the battery for a bit to reset the ECM. I'd also check your PCV valve, and air filter. It sounds a lot like either bad plugs, or a vacuum leak of some kind.
What color was the smoke coming from the tailpipe? Also, how does your coolant look?