For all who run into this and other related problems that warrant replaceing the O2's, whether Upstream (pre-cat, in OEM headers) and Downstream (in -- technically post-- cat) O2 sensors:
https://www.stockwiseauto.com/denso-...an&Model=370Z&
https://www.stockwiseauto.com/denso-...PAQ&ymm_gid=2&
Other O2's that will work...
Nissan 370Z Oxygen Sensor - O2 Sensor - Walker Denso Bosch Delphi NGK Spectra Premium - 2009 2014 2010 2012 09 14 10 12 - PartsGeek.com
Densos are recommended -- in general, cheaper than buying from Nissan, and you can shop around if you know what you are looking for