BTW, this a somewhat common problem with turbo charged diesel's, I experienced the same thing on my 6.0 PowerStroke after installing a larger turbo, the first tune we put on it I had extremely bad surging or turbo stall or whatever you want to call it while going up steep mountain grades , the truck would almost stall it was so bad, 10x worse than my 19 cummins. It took some more work on the custom tune to get rid of it, but we finally did. If you research you'll find the same thing happening on some of the older cummins motors and probably GM and Ford as well. What's happening is the turbo is getting into a state of RPM and compression that is outside it's parameters basically and the turbo cannot maintain a steady boost. This can be solved through better tuning in software, BUT I guarantee what is happening at corporate Cummins/RAM is they are looking at emissions requirements and struggling to find a tune that removes this surging and still meets emissions regulations. The emissions systems on 2013+ trucks is a major PITA to tune around. There is nothing broken or bad on the truck, it's not going to cause reliability issues...it's just plain annoying especially at the price we pay for a new truck!
An EASY remedy to this situation is hit your - downshift button to kick it down into 5th gear and it's gone. This only happens at low RPM <1500 and 12-15 PSI boost.