I do believe the easiest…
I do believe the easiest route of under warranty is everything new replacement if the lemon law does not apply. I am wondering if there may have been recall or there is more than one truck with same issues. I built engines for GM on the line many years and things like this are not usually isolated to one truck, what ever failed on this truck can be traced to time of build, part and who installed it on the line. Most engines at GM with problems like this were pulled from assembly rectified, that’s when things can go wrong.