Hi, yes you may not get much in the way of power increase, and unless you are friendly with a mechanic (obviously I'm not saying this should happen) it may struggle with the emissions test (maybe) but I must say, the subtle change in sound you get is really nice, without a visual chage, like me why don't you go for a broken cat and remove the insides or get one made... cheap and if you go for a cat with stuffing removed it'll look standard.
I don't know, I've done it so guess I'm bias