I am not going to be a huge help here, but I remember reading a discussion about this a while ago. If my memory serves me right, the calipers are not sealed or something like that - which causes dirt and brake dust to get inside and you have to manually clean them every so often. It may not even be the kit you are talking about, but check it out before you buy one just to make sure. Also, the cougar comes stock with an exceptional brake system... So if you are looking for extra performance I don't know how much you would actually get. I am sure they would be a little better, but is it worth the $650? I put cross-drilled and slotted rotors on my car with expensive pads, and I actually think that the stock brakes were better! I still keep them for the looks though!
