They can be painfully rusted in place.  On my 84...I needed a 2 foot breaker bar to break it loose.  Even after that...I needed the breaker bar to unscrew every thread.  When it came out...it ruined the threads.  Fortunately the thread is the same as the spark plug thread.  Ran a tap through it and was able to save it.
If you do resort to heat...heat the thread it screws into...not the O2 sensor.
Z 

     On Thursday, October 1, 2015 10:37 AM, Dennis Jowell <dennisjowell@GMAIL.COM> wrote:
   

 I just started to replace my O2 sensor on my 2.2 wbx. No,luck using my wrenches . Everything is rusted together. The catalytic converter is only about a year old. Is there a better way to remove the sensor? Should I use my touch to heat the sensor ? Any ideas would be great. I might get to Quebec yet just have to get this done.

Regards,
Dennis 

Dennis Jowell
Scotch Hollow Farm
Newbury, Vermont