I sent a 2018 Yukon XL Denali to an independent mechanic today for a pre-buy inspection. His report came back positive with no red or yellow flags. His only negative was a "noise in acceleration" and suspects heat shield vibration, as did the master tech in their garage. A google search shows this is a common problem for GM, and specifically includes older Yukons. Looking for advice about whether this is a fixable problem, or if it's a problem to walk away from. Or maybe it's not the heat shield? Any other ideas of acceleration noise for this model year? They're confident it's not a transmission issue. I live 3.5 hours away so it's not easy for me to hear for myself.