New motor in the truck?
Yup, new motor. I was a victim of Chevy's Active Fuel Management (AFM) and my 6th cylinder lifter got stuck which ultimately resulted in the push rod getting bent and destroying the lifter (which was my fault for driving it with a stuck lifter). Additionally, the spark plugs in cylinder 6 and 1 had oil on them, and cylinder 7 was burning the plugs.
A new motor installed was about $1200 more than to repair/rebuild my current motor, so I went that route. AFM system had to be replaced, which included a new VLOM, new high pressure oil pump, new lifters, new rods, and potentially a new camshaft. New motor doesn't have AFM so I'll always run with all 8 cylinders and it comes with a 100k mile/3 year warranty on all long block parts.