the fan will only be blowing air into the rad im pretty sure (not sure on the rotation of the fan though so it might even be sucking the air out of the rad...) some1 correct me if im wrong

sticking a cai pipe just behind it will only force warm/hot air in anyway, you can place your hand there after u go for a drive and see how hot it can get.

best place would be to have the pipe in the place of the stock resonator then out to the front bar