It depends some headers people claim have actually made there car quieter but generally they don't.
If your going to use a cut out then you might as well just keep the stock exhaust but it wont flow as good as most aftermarket.
As far as the loudness with the cut out open it will make it MUCH louder. I had the same set up with my LT1 that i sold but with magnaflow exhaust and you couldnt hear shit when you got on it as compared to with it capped. |