Hi johnatg
Thank you for this info, I've got the below from Google which make me believe this could be it.
"An air/fuel sensor can read a much wider and leaner range of fuel mixtures than a conventional O2 sensor. That's why they're also called “wideband” O2 sensors. Another difference is that A/F sensors don't produce a voltage signal that suddenly changes on either side of Lambda when the air/fuel goes rich or lean."
I'll give it a try and let you you know.
thanks again!