[kenmosher]

One killer of WB O2s is cold "shock" if you get moisture sprayed on a hot sensor or sensor heater.

Location in front of the turbo can overpower the heater circuit, due to the extreme temps and backpressure can drastically affect readings with a WB (and there's a lot of it before the turbo). I've seen a couple folks do it successfully, but the manufacturer's data says not to do it.

As far as distance from the turbo, shouldn't make much difference, as long as the exhaust isn't leaky upstream of the turbo. The heater keeps the sensor stable (and is critical for accurate readings).

The NB output would work for the factory ECM, although in our application I think it wouldn't really have any advantage over a stock setup, since you probably shouldn't mount it in the stock location.