Story so far, W203 C180 2002 went in for MOT and the CEL came on, code P171(lean system) and so failed due to high emmisions. The bright sparks at kwikfit said the CAT had gone so needed a new one, £700..so I had one fitted at another garage for £350 back to kwikfit for retest, and low and behold failed again on emmisions, but the excuse this time was it was a cheap CAT that caused the fail. Went to a merc specialist who replaced 3 yes 3 alleged leaking vacumn pipes, cleaned MAF as well .No change in the emmisions.So they are now at a loss on what to do next, so I thought I would ask this font of knowledge their opinion.I have a feeling though I shall just scap the car as its turning into a money pit.Thanks in advance.