After convincing myself I need an LC-1 or LM-1 wideband AFR "controller", I then started thinking about where to put it. I'd sure rather not weld a new bung on. The front (narrowband) stock O2 sensor is before the cats, but also before the turbo. I've read that's not a good place for the new sensor - both because of heat (>1300F) and pressure.
I have a cat in my downpipe, so that would cause misreadings if I replaced the rear (wideband?) O2 sensor. But then I got to thinking... if there's already a wideband O2 sensor in the downpipe, shouldn't we be able to read that with the ECU? I've heard "yes". I've heard "no". But I've heard nothing convincing, and am now more confused.
Where does the information from the rear O2 sensor go? Is it truly "wideband". It it good enough to get valid AFRs from?