2006 2500 towing 5500 lbs through North Carolina mountains let me move 750 miles before getting off the interstate to what seems to have gone into limp mode. Multiple random codes when scanned at advanced auto. P0087 code confirmed from a different scanner and no other codes except my glow plug 5 circuit (known). Cleared code(s), offloaded trailer and the truck is functioning just fine without weight behind. Fuel lines under the hood look good, no kinks no long time wear n tear. Will check fuel pressure valve. Any other thoughts? I rarely haul so… quite confused.