I drove behind a nismo yesterday for a good half hour, he had them on and it wasn't overly loud. When he would step on it yeah they were pretty ballsy, but at cruise speed you could barely hear them. We cruised between 70 and 85 mph and they weren't loud at all, just when you floor it.
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I am here:
http://maps.google.com/maps?ll=28.354410,-80.686429
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