I can't thank you enough for posting this. I purchased my 2019 Chev Silverado Duramax late last fall. I have, like you been having this same problem since taking delivery (I didn't experience the issue during my test drive like one of the other posters). Initially, I experienced what I call a stall while accelerating onto the freeway or highway. It happened each time right around 50 mph and lasted only a second or two but was still nerve rattling when it happened. I also experienced the chugging you describe, first around 28 - 30 mph while going through my small town. Lately, it has also been happening at the same speeds you experience. Like you, I have had it to my dealer several times, though the first time or two I don't think they noted it on the service order as I had it there for other issues as well. The last time I took it in I told them to keep it till they figured it out. The put 500 miles on my truck and told me they never experienced the problem however. As mentioned by other posters, it doesn't happen every day and sometimes may not happen in a week (particularly if you are not driving it in the manner that it normally occurs). My wife finally hit her boiling point and called the sales person back and gave him a stiff talking to about how a $70,000 truck should not have these kind of issues. Since that call, the service mgr has called a couple of times and the last time, just yesterday, he told me that the GM field rep had been by and said that officially, GM is not acknowledging the issue as important. He did however, leave him with a bulletin on 2018 a transmission issue that he thinks might be related. He promised to bring a copy of the bulletin by in the next few days. Again, I can't thank you (all) enough for helping me to stop feeling like I am the only one in the world with this and maybe it is somehow just me.