If it's a 2002, are they the same as the 03-07s? The fog lights in my 2003 are easily some of the best fog lights of any vehicle I've ever owned.
The purpose of fog lights aren't to be super bright or project a long distance in front of the vehicle. It's to illuminate the area immediately in front of and as far to the sides as possible. The 03-07 Silverado fogs do this quite well.
For the sake of everyone else on the road, don't drop HIDs or LEDs into your reflector fog housings (or headlight housings for that matter either). Sure, they're "brighter", but they don't put any substantial amount more light down the road than decent halogen bulbs that the reflector is designed for. And they absolutely blast everyone else on the road with glare.
If you actually want more light down the road, then do it right and swap / retrofit in LED or HID projectors.