[Richbot]

Seems like the heater circuit is the problem on the car side rather than the sensor if it's repeated with new sensors, quickly, if that hasn't been eliminated yet

All of O2 my sensors are original and the car has had an Evolve tune for like 90000 miles. Doubt it's the tune. We have thousands of tuned M3's out there and eating precat O2's is not such a common problem unless they're all hiding out where the people with catastrophic DCT failures are hiding, and multiple inexplicable failures is definitely not commonly reported on here

A) try a genuine BMW replacement, just to make sure, sometimes parts get transposed and marked wrong and it could be a bad lot and you're buying from the same bad lot over and over
B) troubleshoot the car side of the heater circuit

Not necessarily in that order, that's what I'd try, if I was just a dumb guy in a home garage with a scanner, which I am