Hi I'm wondering if you have an aftermarket dump pipe? I've heard of O2 code that is quite random and difficult to be rid of and is generally associated with aftermarket exhaust mods. If there is a possibility of a firmware update resolving the issue I'd suggestit's a good idea to get mazda to do this - backup your tune, return ECU to OEM spec, take it to mazda for ECU flash update - or at least check one is available (probably is), then restore your tune. In addition I've heard that shimming the O2 sensor - in doing so pulling the sensor back a little out of the exhaust flow - can do the trick.
"Blue Meanie" 2007 Aurora Blue MPS 3 - 18x8.5+44 SSR GTX01 - 235/40R18 Michelin PS5 - 3.5" ETS TMIC - CPE stg 2 mount - HKS/CPE BPV - 2XS inlet - 2XS short shift - Corksport turbo manifold - HT 98 octane tune - Leather/Aluminium handbrake - Momo shifty knob - 7" touchscreen - JDM Mazda Retractable dashtop screen assembly - Bespoke Raspberry Pi Android based GPS/Carplay and instrumentation - 36AH reserve battery and C-TEK isolator - TEIN Street Advanced coilovers 1" drop - Superpro bushings - 220Kw/410Nm.
"Lipstick" 2013 Velocity Red MPS 3 - 18x7.5+48 Enkei RPF1 -225/40R18 Federal RS-RR - CPE TMIC - COBB inlet - CPE stg 2 mount - COBB Stage 1 98 octane tune - COBB shifty knob - 2XS short shift - 2XS turbo manifold.