That must be one restrictive exhaust/intake from the factory! Now I'm curious what all of that would do along with a custom tune.
I've had Corsa before on a V6 and there wasn't even a hint of drone, so I'm curious to see how it does on this CTS. But more important, how does it sound inside and out. That was my only complaint with the Corsa + V6 combo... it sounded like a 4 banger.
On a V8, they just sound mean.