MOT failure on emissions

[S6 Devil]

My Tuscan had it's S spec engine rebuilt by TVR Power in July 08 and has since been having a full bodywork and interior restore so I haven't driven it nor has the engine been run under load since rebuild. It has just gone for an MOT and failed on emissions.
It failed on both the O/S and N/S exhaust emissions, the lambda readings after a second fast idle being outside the specified limit. The carbon monoxide content was also excessive on both. Also the N/S CAT needs replacing. The engine has also been overfuelling meaning when the repairer has tried to start the car, he has had to remove the spark plugs as there is excessive fuel there, in order to get it started.
I had two new cats and one lambda fitted when the engine was rebuilt. The cats are under warranty so that is no problem. Can anyone suggest what may be the problem about the lambdas, overfuelling and exhaust emissions?
Thanks.

Edited by S6 Devil on Saturday 14th February 11:43

[supercopa]

did you have a software mod on your car's ECU when rebuilding?

[S6 Devil]

supercopa said:

did you have a software mod on your car's ECU when rebuilding?

I don't know, I could ask Dom!

[rralston]

Yep - have a chat with Dom to see what his point of view is.

It could be that one of the lambada sensors has broke. (they do quite regularly) This will confuse the hell out of the ecu and it usually means that the car will run like a sick pig. This could be causing the emissions failure.