I have SZ exhaust from turbos back to JWT Genie catbacks. My car idles and cruises exceptionally quiet. A TT in town has non-resonated B&B catback with SZ exhaust and it is appreciably louder. Not as bad as an NA, but if you want a car that only sounds great when you are really on the throttle you should either find a quieter catback for guaranteed results, or throw on big resonators with the SZ catback and see if they get you the desired results.