Mystery noise found. I think.

But today while drying the exhaust tips after washing the car, I smacked the bottom of the bumper with my hand and heard the noise. Turns out the bumper support isn't held in there too securely, just a few of those push-in plastic clips and can be moved around quite easily.
I was thinking about replacing those plastic clips with some self-tapping screws. Anyone else have this problem and what did you do to remedy it?


