I built the entire kit myself. I don't have any sound but the car is very quiet. You would never know it had a turbo till it surges when I lift.
Even under boost there is no turbo whistle. Low boost rules. I will be changing to dual 3" tailpipes soon. 2- 3" dynomax bullit mufflers and 2- 3" dynomax ultra flows. I like my car quiet. I can hear the engine if it pings and the stereo when it sings. Loud doesn't mean fast.
I killed a 13 sec open header bracket car by 30mph and he never saw it coming. My buddy said he couldn't hear my car at all. Only when I shifted and the turbo sneezed.