MOT Fail - Emissions

[SnapMonkey]

On Monday, the brothers 182 failed due to exhaust backbox leaking. Fitted new (genuine) backbox, retested and failed on emissions, one of the readings was 100x over apparently, didn't see which one though.

Going for diagnostic tomorrow morning, but is there a list of likely culprits to be checked first? I have searched but theres literally thousands of threads with fail and emissions in!

Thanks in advance.

 

[Paul182]

mine was twice the limit the other day on CO turned out it was the k-tec sports cat standard on and it flew through !. might want to try the lambda sensor