I will be doing this shortly, once i get the funds, I have a Bilstein B12 Pack sorted for April first, then the Sports CAT and then a Remap. I had a good chat with the guy who fitted my exhaust and he said that you do claw some BHP back due to removing the restriction to a certain level. He reckoned the best way forward was to Decat as the Lambda sensor is before the CAT, and he thought this alone would gain back 10 lost BHP (assumption) by removing the restriction all together (Obviously MOT issues). so a sports CAT is obviously going to be somewhere between 0 and 10 BHP gain (assumption).