I had the JCW PRO exhaust installed on the GP yesterday and it really has improved the sound of the GP! We took it to Louisville and had German Tech Autoworks install it and it included the installation of the JCW carbon fiber exhaust tips. It looks great and the sound is awesome. I ordered a custom holder from Hong Kong to hold the activator for the exhaust, but it is somewhere in transit. Paula led the backroads trip home in our JCW and I followed in the GP. I was unable to really notice any power improvement, but it sure made a difference in the exhaust note. It is a raucous and wonderfully deep, and throaty sound and a roar when you really put the go pedal down. I had warning light appear in the panel about a misfire that could damage the catalytic converter was the only downside to the trip. We are going to schedule a trip to Mini of Cincinnati to have that corrected. Alas, that is not a fun trip as the traffic there and back is abysmal at best, but it is a necessary trip. I/we do love the GP, it is a handful, but the more we drive it the better we like it. It does take some getting used to as it has its quirks, but they are minor compared to the fun and performance factors!