I want run on my z6 turbo a custom 2,5 inch exhaust with a Vibrant ultra quit resonator and Vibrant streetpower muffler.
I never heard them in real because they don't drive here in The Netherlands.
But is it much louder than a stock n/a car?

 

theres a noticable difference.. stock is quiet and restrictive

 

I have the resonator and the black streetpower muffler. It was loud before the turbo, but once I put the turbo on there, it quieted down a bit. It's louder than stock, but it makes a great sound and it's not ricey.