My V70 D5S recently failed the MOT on emisions.A couple of indipendant mechanics thought it might have been due to the fuel i used.(supermarket).The good news is the car passed after some 'gunk' was fed to the car.Any advice welcome.
same happened to my last car. a 307, it failed its mot so mechanic took it for a short drive to warm it up then is passed. i have a cousin who is a mechanic who i told about this. his reply was he would never fail a diesel on an emissions check as so many diesels were hit and miss, especially if tested when cold.
i wouldnt worry to much about it.