2018 cascadia cummins noise

I've got a 2018 cascadia with an x15, 450/1650. About 150k miles. When pulling i get a loud noise on the passenger side. Usually at 1400 rpm+. It sounds almost like a train chugging. I've also heard it described as the sound of ground coffee in a tin can, if that makes sense to anyone.

My mechanic looked it over. Said he can't see anything that would be an issue. Said I'd doesn't sound like a valve or anything. I've added a YouTube clip. In the video it might sound like the truck is shaking but its not. Its just the engine chugging making that noise.



I just wanted some advice before I go spending an arm and a leg at the cummins dealer.

 

Really? I also have a pacar, and have owned a volvo and cat engine in the past. This is a first for me.