Steve

They are identical, post cat is the one prior to the back box (post or after cat) most likely you have an aftermarket cat and just one momentary blip will actvate the engine management lamp, I get the same on a long run (fed up with reseting) so I have a mil eliminator from elise parts to fit. I got a replacement (bosch) Lambda from MGF n TF bitz when I changed the cat.

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