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                         Could anyone help me to diagnose the above, it's failed on both low and high idle test with the following numbers: 
Low idle: 
CO 0.79% Vol (above 0.30% fail) 
HC 240ppm 
  
High idle: 
Lambda: 1.02 (pass, between 0.97 and 1.03) 
CO 0.80% vol (above 0.20% fail) 
HC 238ppm (above 200ppm, fail) 
The choke warning light has perpetually been on on this car (or is it the Lambda sensor light?)   Car had a new catalytic converter fitted about 6 years ago. Mileage is currently at 186k miles. 
There are no untoward sounds coming out of the exhaust, so I don't think the exhaust is leaking.   Could this be a simple fix like a bottle of Dipetane, or else a new Catalytic converter? 
any help appreciated, thanks 
                            
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