I've seen this a few times, actually thought about buying it at 1 point cos he doesnt live far from me. I wondered if it was the motorsport manifold but i soon realised it wasnt when i saw a pic of the standard one and they were identical!
In case its not removed, i just sent him this: not sure if i am correct on the cat cell thing?
Thats not a JCW manifold, JCW dont make a performance manifold only the MotorSport lot do for the Mini Challenge cars which is a 4-2-1 pipe work manifold.
Yours is a standard Mini One, Cooper and S of the R53 range from 2000 to 2006, its a 4-1 manifold and has a standard BMW 400 cell cat.
With the cars that came with the JCW kit i.e. exhaust etc they only include the exhaust section from the cat back, so as they didnt make a performance manfold they kept the same standard manifold and cat as thats on the rest of their range.
So im sorry mate this product has a fauls description, it will not make an extra 20bhp, but could potentially lose someone hp depending on what condition the cat is in!