tony said comptech bolts up to the stock cat.
toda comes with test pipe and needs cat welded to it, TODA can do it as "akina" has done it.
Yes, RT cat is ideal but is not viable with Oz $$$ sucking dogZ ballZ!! :p
Metal cat would be nice but still quite expensive too.
But if you have the money to waste then go berserk and goo for the top stuff....