Mine chucked a CEL when the Berks went on, the extenders did not resolve it for me, I believe it has for others. At something like £12 I think they're definitely worth a shot. Got mine from Clark Motorsport on here, so you can shoot them a PM. They're always happy to help.
Ultimately, an Uprev "cured" the CEL for me - when I say cured, I mean the sensors were disabled. I think GM also cured the issue the same way. I can't imagine you want to fork out for an Uprev though. Best bet is to try the extenders first and then failing that, get a cheap OBD2 code reader and just check it if it pops up, clear it, then lather rinse repeat as needed.
Edit: some threads on the same topic
http://www.350z-uk.com/topic/77029-help-recurrence-of-o2-sensor-eml-with-new-codes/
http://www.350z-uk.com/topic/64569-error-code-p1147-heated-02-sensor2-whats-the-next-step/
http://www.350z-uk.com/topic/58158-error-code-p1147/
http://www.350z-uk.com/topic/61395-my-first-cel-light-p1146-p1147/
http://www.350z-uk.com/topic/61136-airfuel-check-light-since-uprev/