My 1996 outback barely failed smog so I've decided to change out the sensors, change my oil and plugs and run some “guaranteed to pass smog stuff” 

I ended up breaking off the rear sensor but its a very clean looking break and can be welded back on the cat. Any ideas on how I can separate the sensor from the cat part? Ive tried heat, ice, wax, pb, etc, etc

PB or Kroil. Make warm first. vise on O2 bung  ( you can buy replacements cheap if needed), and wrench on sensor.

O.

Buy a new bung. They are cheap.

On the floor, I put the bung into a pipe wrench facing up, slide a box wrench onto the sensor. Put a piece of wood under the wrench to make it set level. Get the wrench tight and tap it with a hammer. The shock will loosen it and then it usually turns off by hand.

CowaBUNGa!! Mission accomplished. After working on it for half the day, I became frustrated and reached out for help and sure enough soon afterwards it busted loose. I think i tried all your suggestions and not sure which one worked, but I appreciate  your help.

thanks

Great...

It's a shame something so simple has to be so hard, but it's a great feeling when it's done.

Half a day for a $5 part. Congratulations on accomplishing nothing.

GD

^ Unnecessary.

It had to come off whether a new one was to be used or not

O.