Engine runs rough when warm and towing
My 97 F250 has developed a problem in the past week. When I'm towing my enclosed landscape trailer, and its warm and a couple miles into the trip, the engine begins to miss. When I stop at a red light, the rpms will fluctuate up and down between 600-950. I replaced my cps with a navistar unit last month. Fuel filter was replaced about 6000 miles ago. Truck has 198,000 miles. Oil level is ok, and I'm not getting any smoke.
I took the truck out yesterday and it started acting up so I parked the trailer and even when just driving the truck, it was still acting a little different. Once I got finished on the job site, an hour later, I drove the truck home and it seemed ok. Any help would be awesome and greatly appreciated!