Q: Loss of power

My car was driving perfect untill i parked it for a couple months. When i went to drive it i noticed that my car was hesitating every time i went to acceletate. After about 10 mins i decided to give it a nice amount of gas and try to take off fast as soon as i did a huge cloud of grey and white smoke came from the exhaust but it only lasted for a min and quit smoking. Ive continued to drive it a little and will only smoke a lil if i push on the accelerater hard enough. Has a huge amount of power loss though doesnt like taking off or maintaining high speeds. I had a check engine light check done at auto zone they told me bank 2 o2 sensor was reading bad i went to replace it and noticed that the pigtails connected to the sensor was not conected and looked cut. I was also unable to get the o2 sensor out and still have not replaced it but the car is currently sitting. Im wondering how long its been lilke that? If it could be just the o2 sensor or if its clogged the catalytic converter?

My car has 200000 miles.
My car has a manual transmission.