Hi Hugh,

No one knows everything, except maybe Known BS artists running for president.

MAPP gas can be used by Driveway wizards to heat stuff so it gets loose.
MAPP gas is hotter than propane
but not as hot as Oxy/Acetylene

You can get it at Home Depot, Lowe's etc. and maybe even Walmart, Its in a yellow
canister and it's more pricey too. Plumbers are using MAPP gas now since it heats up stuff faster. If you don't have a torch in your lool arsenal then
maybe now is the time to get one. I like the Benzomatic with the push-button starter which is fabulous as you don't need to mess around to get the torch lit.

When exhaust bolts and O2 sensors are welded stuck, heat is the savior.
Get the subject red hot before trying to bust it loose.
This is especially important with exhaust manifold and flange bolts that have a habit of snapping off instead of unscrewing....get em red, and try to bust em loose...not too hard , if they don't start, give em more heat, it takes time.
It's better than having to drill out some snapped off bolt.

Post back with your results with the O2 sensor. Perhaps it will just screw out
without any series of grunts and curses coming from under the car?

Bill