Two things first. One, the dealership I took my warranty covered truck to is packed chock full of idiots. Second, I love my new-to-me truck.
About my truck. It is a 2020 Silverado Work Truck, single cab, long bed. 5.3 and six speed automatic. Being a work truck trim level it has am/fm/cd with backup camera, PW/PS/PB and cloth interior. On to the problem. I bought the truck 18 months ago with 10,600 miles on the odo, it now has about 26,500. Since I picked it up and drove it home it has had a slightly rough idle. No codes live, pending or stored, once in a while I can feel the same shudder/roughness at steady highway speed though that is pretty rare.
Idiot at the stealership said "I don't feel it", after I pushed hard it was "this is normal", when I laughed in his face he said "If there is nothing in the computer, like a DTC, my technicians can't figure out what is wrong".
I know, I know. A slightly rough idle isn't a huge deal but it bugs me. My wife's 2013 Highlander idles smooth as silk, my 1992 Chevy 1/2 ton TBI 350 idled smoothly. Geez, I have a 1967 Olds Toronado that wasn't started for about 20 years that started and runs smooth.
Any help and suggestions welcome.

 

try a different dealership, or if that fails, call Chevrolet national customer service and complain