Ok. I thought I'd update this post just for an fyi.
I took Kens advice and before upgrading any headers and such, I just took it in for the warranty cat 1 code. (check engine light) The dealership replaced the catalytic converter on the drivers side. I'm driving along 2 days later and there's the light again. Now they are replacing the vent hose and overflow cannister. I'm hoping that they were smart enought to order a new gas cap while they're at it, since that thing has always given me trouble.
While I was waiting for the cat. to show up at the dealership, I took a little off road trip and blew out the front differential. That was scarey! Come to find out, when I got it to the shop, the tech says, "oh yeah, remember when you had us change the oil before you went to Moab? You had a crack in the front diff. then." So now I've learned that GM doesn't recall problem parts, they just wait for them to fail first. I'm glad we bought the extended warranty! I'd be shelling out $1500.00 for the repairs. They also told me that this is something they knew about in the older models, but since then has been fixed. Newer models shouldn't have this problem.
So, if this subject hasn't been visited in a while, I hope this helps someone else.
Happy Trails!