As long as the entire exhaust system is stock then that's just the way it is. If someone changed out the mufflers for something else (Flowmasters, etc..) then it will sound like crap. They came from the factory as quiet as possible to avoid drone at certain RPM's. And these motors don't normally sound any good with any type of aftermarket or "upgraded" exhaust. I've heard a handfull over the years that sound "ok", but your're never going to make it sound great. Just the way it is on these V6's.