I hope the cat knocks out a bit of noise since we have some strict noise laws down here too. Fortunately most of the police turn a blind ear to a Cobra
I think the cat will act as a flame trap and stop the foot long exhaust flames on deceleration. I don't know if this is a good thing or a bad thing.
Hopefully I'll be able to hear what they sound like befor the end of the year.
Cheers