The lambda sensor is the green one at the back of the engine bay. it is attached to the exhaust manifold and measures the O2 or CO2 levels. it is easy to change just undo it and put the new one in.... they are expensive for what it is.. about 40-60 quid..
Mine is fine, it only had a mot last week and it passed the emissions test with flying colours.
The air box is good though. it has made a difference, sounds better, the throttle is quicker to respond.
Think that i might try to put a direct air intake on. may have to have a think and try some stuff out..
Has any one out there done it befor??
Any probs???
and do i need to do any thing to the ECU?? :-D