If I remember right, the rear sensor has a yellow heat proof covering on the wire and the front has black heat proof coating.

Ask your mechanic if which colour it is. I might be wrong in thinking the rear sensor is behind the cat, it might be just in front, its been a while since I've looked to be honest

 

in one post you say just after the cat then in another you say just before the cat ???

i think you need to find out exactly where it is before you go buying one

 

I mean if your looking at the exhaust front to back it would be before the cat, sorry for the confusion!

Quite a bit of difference in price between the two sensors

 

http://i229.photobucket.com/albums/e...st-diagram.gif

this shows where the sensors are located

o2 sensors (lambda)

 

Mines def the front o2 sensor then according to that diagram, as you can see it by looking in from the engine bay, well see where the rac have disconnected it

PS. mine is a non turbo model