I have them on my car. They were there when I bought it. The exhaust is a nice setup with an X pipe and some mellow turbo mufflers. The cutouts are electric than can be set from closed any amount open. Do they make a difference? Beats me, I haven't had the car at the track. But, it's a cool attention getter when cruising and puts a big grin on my face when I pass a group of Harleys at speed. They seem to hate that for some reason.
