CT4v Blackwing Custom Cat Back Exhaust? Anyone done anything Custom? Results?

[Rob CT4-V]

Is there really any power gains from a catback on these cars? Or is it strickly for sound?

I ask because I had a Corsa on my 04 GTO and went back to stock and only lost about 5rwhp, that was when I was around 430rwhp. If you looked at that exhaust you'd think it would be so restrictive but it actually flowed very well. I'm thinking it's the same for these but haven't seen any dyno's to see the comparison.

 

[XTRMLN]

I would assume not... I have since done tapouts' DP's and per their info Hp gains are super miniminal unless you unlock with a full tune. So I would think a catback system would be the same.