I hear it in my car too, just I don't hear it that much. Thanks to being a drummer/guitarist for so damn long
My wife's not said anything about it, so maybe she can't hear it?
I do notice that after I've been in the car for a while (longer drives) that my hearing is just as whacked when I get out of the car an in my house, as when I've been riding my motorcycle for a couple hours, and I've got loud pipes on it.
My Z is stock except for the G3 intake - catback coming soon, and I'll probably go to longtube headers once they are out