99 XJ Noises

At first I got a noise when I had a fast stop going down hill at a red light. Sounded like a baseball card in a spoke of a bicyle. It has progresses to whenever I hit the brakes or decelerate w/o braking. I pulled the tires off and inspected the brakes and calipers but I find nothing out of the ordinary. The sound seems to be coming from the center or center right front of the XJ. Any thoughts will help greatly.

It could possibly be the chain in the transfer case. That is what mine is doing right now. Looking for a cheap kit.

Sure you've checked this already, but there aren't any wires clipping a fan at all? That happened to me once. Does the braking feel even or choppy when you slow down? Could also be a warped rotor hitting the caliper.
Hope it helps.

Out there guess. . .
Check your O2 sensor harness for your Cat. isn't hitting a U-Joint on your driveshaft.
Or anything else next to a rotating part.