2004 6.0 excursion.
Truck will drive around town with no problems. Has good accelerator response. after about 10 minutes of driving at >70 mph, the truck will begin to decelerate. Speed will drop to 50 mph or less and RPMs will not get above 1500. Additionally the engine has a rough run feel to it. Feels almost like LIMP mode. Pulled the truck off the road and press the brake until the truck came to a stop at which time it stalled. Waited about 5 minutes and restarted the truck. Problem is intermittent. Currently the truck drives around town with no issues. Have not had it back on the highway.
EGR is new
Filters are new
Any suggestions would be a great help