SM370

I have a 2018 Silverado crew cab with 5.3L engine and 6 speed transmission with 25000 miles. The truck has what seems like a misfire and rough stumble while driving 25-40 mph while the engine is cold, not up to 210F. The issue is present when in 4 cylinder or 8 cylinder mode. I keep it in L (keeping in L5 to stay in 8 cylinder mode) until the engine comes to normal operating temperature and then the problem goes away. I took it to the dealer and they could not find anything wrong or duplicate the problem. There are no error codes identified or problems noted. The problem is more prevalent in cold weather, but is still there at Louisiana summertime temps. Anyone else seen this? Thanks, Gary

Are the mirrors still available? Asking price? Thanks, Gary