Lamba Is my guess.
Thanks for your PM Simon, I live in Appleton, just past Botley, if you know it?
I know Oxford Car audio, may pop in soon, need a alpine-renault adapter to get my steering wheel controller to work the HU......you got them???
I have a fuel/air ratio tester if you need to test yours, and also a Snapon scanner we may be able to use.......the scanner tests all of your sensors & temps ect.
there is a link here somwhere on cheap lambda's