sometime the car has a real rough idle to it when im backing out of the garage. usually quits before i can get out of the neighborhood.. anything i should be worried about ?

 

Has it been scanned for codes? If it idles rough and and stops it sounds like it could possibly be the egr. I would think it was a vacuum issue but you stated that it wasn't constant. Does it fluctuate at all? When was the last tuneup?

 

I'm pretty sure that's a common trait of the LS engines. My Corvette did it, my 2010 Camaro did the same, and my 2012 Camaro does it. I wouldn't worry about it, but as someone mentioned, check the codes and if you have serious concerns, take it to your Chevy dealership and have them check it out. I put a Cold Air Inductions CAI on my new Camaro and the rough idle at start diminished.