I personally like the way the 18 GT sounds ( no active exhaust option) compared to the 15/17. I’m not touching anything. It sounds better then my C7 GS with active exhaust on its track setting.
Do you have to cut the sound tube to do this, or is there a break in the tube where you installed the valve?OP, another option is a $5.00 valve. Located here: https://www.mustang6g.com/forums/showthread.php?p=2128317#post2128317