C02 emissions?????

[cb10]

Had the car moted today, had to put my standard cat on and also put a new 02 sensor in. Came to the test and you are allowed upto 0.20, mine read upto 7 and nothing below 5.65.

Anyone any advice what is wrong as this is major high. Its def been running rich for a good few months now as its smells quite abit sometimes?

Any advice would be great.

Cheers craig