2011-13 gaps weren't checked and plugs just tost in as is pretty much on assembly.I just pulled my plugs the other day, to see what they look like, and up the gap to .030. Getting way more power now, and boost has gone up. I bought the car at 18,000 Km's, so it didn't really need touching but I figured I'd look anyways. It surprised me to find that all of the plugs came out at .020 gap, when that's a lot smaller than what even GM specs for the plugs. What happened there?
Wait you are a 2015 the PO or dealer may have done that to you. I had a new coil pack and plugs put in my car they had my gaps not to far from what you had. I ended up swapping plugs and gapping them what you did until I got tuned. gaps went back down to 0.028 then.