21 LT Trailboss owner here. 5600 miles, Check engine light came on P0300 - no felt misfire. Took to dealership, light was off, tech ran history showed the pass-fail and 1800 total misfires (not many). They changed my oil, rotated my tires and updated my infotainment.
Pisked it up, and in the way to work CEL started flashing and turned off after only 5 seconds. Again, no felt misfire. Took it right back into dealership after work. History showed bank 6 had 12,000 misfires. Opened up and bank 6 lifter was collapsed. Replaced all 16 lifters with the new(improved?) lifters.
My dealer and tech were great.