The problem with using a Heli Coil is that the hole gas to be drilled
oversize to accept the fix.
If the threads are mashed, either run a thread chaser, or a 18 mm x 1.50
tap into the hole.
Either one will usually give you enough usable threads for the new oxy
sensor to grab onto.
Don't be Charles Atlas when you crank the new sensor down.
I just replaced mine this evening, and the threads were toast.
They came out and left the threads from the old sensor in the converter.
I ran the tap right into the hole, loaded up the new sensor with high
temp anti seize, and it ran in the converter just fine.
20 minutes and it was all over.

RC