The early 5.7s also had valve seat problems. Not common but they occurred enough for me to hear about it. A loose valve seat could dislodge, reseat, etc until it falls completely out.
My 2007 Ram had an MDS lifter fail at 59,000 miles. It would hang partially open, causing a misfire in that hole and contaminating the mixture in other cylinders as the piston rose to TDC (When the valves should have been closed)
The 2003 and up trucks had MDS, right? Mine was intermittent and then went full AFU. THey had to pull the head to get to the lifters. They also pulled the rod and piston to hone and install new rings on that piston.
Lets hope that yours is something simple.
Bad o2 sensor could cause problems. Good luck.