I'm sorry to hear that man, that sucks : (.
I was able to speak to GM as well and the Customer Srv rep said he spoke with both dealerships and has taken note of all my concerns (engine issues further down the road, especially after my warranty is up), and communications. They said that I should just keep driving it and if the sound gets louder at all to take it in and go from there. I was left feeling "Ok, if I've got several service techs saying that the problem is not huge then maybe I can live with it. And if it gets worse, then I have the backing of GM to get it fixed"....
But your post makes me a little fearful of if this contact with GM Customer Service actually does anything to help out (since the resources promised to you weren't there) or it's just to un-ruffle feathers temporarily and all a PR show.
There's still the issue of my onstar lights coming on occasionally while driving (picture link below), the gauge bezel breaking (I've been told fixing that involves taking the entire dash apart so I'm not sure it's worth the risk of having a rattling dashboard the rest of the life of the car), occasional rattling from rear seat, and the VERY rough shifting when the transmission is cold (and once a month grinding despite the clutch being to the floor).
I have decided though, that I am going to go get the engine Dyno'd, and if it's making any noticeable amount of power less than it should be then that tells me the engine issue isn't small and harmless.
Obligatory Conspiracy Theory given recent events: Maybe the lights are on because the NSA is listening to me.... Next time I see them on I should ask them for a Job lol