Part 2: 2018 Silverado P2635 code - everybody is stumped! Should I just tune it?

Truck was dropped off Tuesday afternoon, but as of Wednesday the dealership can't seem to get the P2635 code to come back - no matter what they do or how hard they drive it. I'm at a loss as to what else I can do to remedy the issue. I spoke to the service manager and mentioned that I wanted to tune the truck to see if adjusting the timing and fuel maps would help. She didn't quite endorse the idea (I'm sure that legally she isn't allowed to), but did agree that unless they find something by lunchtime tomorrow, tuning it to compensate for the aFe intake might solve the problem.
As soon as I have a better handle on what I'm going to do with it, I'll post another update. At this point I'm leaning toward getting the tune knocked out and hoping for the best. What do you guys think?