Now that the '34 is running and while was troubleshooting some closed loop idle issues it became clear that the original O2 sensor was getting lazy.  The key indicator was that it would barely go below 300mv.  Replaced it with a new Bosch #13117 sensor.  These new units feature a much quicker heater warm up (about 10 seconds), lower heater current, and less prone to contamination clogging.  After installing my mating plug it should have been a screw in operation.  Of coarse nothing ever goes as planed.  The hole in the exhaust pipe just inside of the bung was slightly too small to allow the larger head of this new sensor to fit.  Several hours of hand filing I was able to open it enough to clear.