It will hurt top end power.
Again, I want to SEE proof. Something concrete.
Surface area increases at the cat, and I believe enough that it compensates for any restriction.. which is why I would like to see dyno evidence. Location in the exhaust plays a part as well.
I can see the potential for hurting top end power.. but does it really? and if so I want to see by how much and at what power level? At what point do you maybe need to go to 3" system (V8)