http://fordfiestast.co.uk/ubbthreads.php/ubb/showflat/Number/240669/site_id/1#import according to this it is a small difference. But if it would be a hassle for you to change before MOT it is best with sportscat I reckon. I have a milltek system with sportscat and is well pleased. only thing I have to do before MOT is to change back to original map. When I have the Pumaspeed 180 map the car fails on the MOT. So it is to high emissions.