Get used to it Rob. It's "today's" Chevrolet.
My Silverado makes more noises than my '94 K1500 did with 266,000 miles on the clock. What pisses me off the most about it is I could've bought 10 K1500's for what I paid for this thing.
But anyway ...sounds like it's definitely exhaust related. It's the only place where things expand enough to stop a rattle, besides inside the engine. Mine has noisy lifters & piston slap when cold too.