The O2 sensor as far as I know should not cause your car to be sluggish.

All the O2 sensor does is monitor the ratio of polluting exhaust and air exiting your motor in order for the cat to clean it up before spitting it out the tail pipe and into the environment. Basically if the level of pollutants is too high the o2 sensor will cause more air to be added to the mix which triggers a reaction in the cat to clean up the exhaust.

Is there a problem with your O2?....Maybe

Is it causing your car to be sluggish?... it shouldn't be