In further playing, I moved mine about 5' down stream from the turbo, and it reads just a little richer there (maybe .2 AFR).
I think long term, that might be the better spot.
Being further away means the sensor is just running on it's heater and not as affected by EGT.
Also, there probably is slightly less backpressure where mine is mounted now.
I have the ATR single shot with the pitbull where the converter used to be, and an ultraflow where the Pitbull was designed to be. My O2 is 1.5' behind where the converter was (pitbull is).