Next to a rumbling v8, your not going to hear a thing..our montes don't really get much louder even with straight pipes and a glass pack unless you have crazy work done to it like Zippy's monte.
This is actually a SLP cat-back exhaust system..Its fairly loud when you get on it, but at idle its quiet. Now remember...these two videos your seeing (Keane's and mine) We both have superchargers, it kinda deepends the sound a little.
I've heard flowmaster 44's on a impala with the L67(supercharged) and they have a nasty metallic tone to them..