Where did you get that from m8? :?
Ive got one, and if its the same, its 70mm all the way through, with a small silencer in place of the cat, 3,5" slash cut, with a black back box that says prof on it?
No idea about increases in performance, but IMVHO, they sound the absolute tits, not overly loud inside the car, but pretty noisy outside (especially if you remove the middle silencer like me), quiet off boost, no "drone" at all at motorway speeds (unlike some other exhausts), i wouldnt swap mine for anything.
If you cant weld it up, or deceide that you dont like it, i may be interested in buying it off you for spares m8
lol, just noticed, the postage may be a bit :?