Get the decat from NW performance I had the single lambda cat and bought a twin lambda sensor decat and it fit fine, all you need to do is look at your cat if there is a lamda sensor just before the cat joins the midsection then it's the twin lambda cat you have, so get a twin lambda decat from someone.
If it's the single lambda cat you can get any decat all you go to do is buy a bung for the second hole in the decat.
NW performance decat was fantastically well made (for a bit of pipe) and cheapest I could find on here as well