A fair amount of people on this site have a muffler of some kind, mostly just to have a conversation in the cab, or to not deafen any passengers they may have. But back to the main topic, I do not think it would have much effect performance-wise or even with EGTs post-turbo unless it was highly restrictive, and I do not know of anyone who installed one and then regretted it later for having said issue. I'm sure it would not be that much of an ordeal to swap out your included muffler with a 3.5 or 4 inch straight-pipe to compare how it feels, but seems it would be a moot point given the weight of the trucks vs. rated power and torque.