Decided to clean my O2 sensors with this same method, rather than using gasoline on the sensors. I figured if the light acid wash was good enough for the catalytic converter, then it should be fine for its partners in crime (the O2 sensors). I used a half gallon of tap water instead of distilled. I cooked for two hours, scrubbing occasionally with an old tooth brush. Pics:
BEFORE (upstream on left, downstream on the right):
The downstream one on the right was throwing the P0420 code.
Submerged the contact area of the sensor only:
After cooking (no boiling) outside for 2 hrs, compare the above and below photo to notice the flakes of yellow and black in middle of the pot that have gathered there due to stirring:
AFTER (upstream on left, downstream on the right):
Took it for a spin of maybe 15-20 miles. All seems good, Felt like I got into DFCO easier, sooner, but that could easily be confirmation bias. Butt dyno stuff, that.