[Martin Cox]

Likewise, at the end of July, my 20 year old V70 Tdi Auto with 223,500 miles passed without any difficulty at all. Although the vehicle is fitted with a catalytic converter, it's the original, and I don't think it's a terribly sophisticated affair anyway and it won't have any effect on visible smoke and particulates. It certainly predates the DPF. I understand you are allowed up to 6 accelerations to get within the required smoke limit. Only one was done and that was comfortably within the limit.

Although I don't recall ever seeing it written anywhere, I understood that generally a vehicle was not expected to reach a higher standard than it was capable of when it left the factory.

So in answer to the original question, I don't think it shouldn't make any significant difference to any older but well maintained car that doesn't have any modifications now deemed as MoT failues; such as non factory standard headlights or missing DPFs

Martin