I also had the de-cats installed, have been traveling too much to really get a chance to take any clips like I have been meaning to do... But, I will say this - that the de-cat makes the throttle response better off the bat, it feels "free-er" flowing, and stronger, and I think the sound really isn't much louder, it wasn't noticeable. But my wife says it is louder, its really not. I just am always stomping on the pedal with my mods (BMC Air Filter/De-Cats/ DBW/ECM/Springs) - The car is much faster and meaner than before, haha.. So, no contest there. Definitely the best power upgrade for the dollar value I think. I kept my stock exhaust, if I drive it in sport mode its already loud, so I keep it in non-sport for when I come around the neighborhood, although sometimes I like to keep it in sport when I want to announce that I'm home, haha..