First time poster... 2005 S40 T5 AWD

Trying to replace my rear O2 sensor, it failed and have had some misfires and such the past week.
I bought the bosch replacement part that you need to splice in yourself, simple enough but cannot get the O2 sensor out. Tried letting the car run for a bit to heat up the bolt/thread and still couldn't get it out, and hit it with a torch see if that would be enough to let me loosen it up, but still can't get it to budge.
Any suggestions or is it time to hit up the garage?

 

Guess if you can not take it out on your own then you should see a mechanic.BTW the rear sensor will not cause any backfire its only checking the CAT.The front one on the other hand will do just that so the question is how did you figure that you should replace the rear one?