Not to throw a wrench in this but we just called our dealership because we were interested in adding fog lights also and they informed us that adding them would void the warrenty. since GM does not offer the addition at this time it would be considered aftermarket. Just wanted to throw that out there incase nobody knew.
it's their way to getting everyone to upgrade to a LT.[/QUOTE
In the US, the Magnuson-Moss act strictly works in our favor. They could not void your warranty for adding it. The only way to deny warranty coverage is if the addition of the fog lights caused (and they would have to prove this, the burden of proof is on them) a related component to fail. Then only this component would be denied warranty, your overall warranty would still be in effect.
I'm hoping using all GM parts would make this a slam dunk.