Had the truck for about 2 months. Pulled the job trailer twice about (4500#). First time on slight hill while accelerating I got the engine code for a bad EGR. A couple cycles later it went away. Today was pulling up a slightly steeper hill locked in 4th in tow/haul with exhaust brake on and lost power. Downshifted to 3rd ...Nothing. barely hitting 15mph with foot on the floor. Pulled to a stop, truck started lugging for a couple seconds. Saw a big cloud of smoke out the exhaust,gave it a lil gas and it started running fine. No problems without trailer. Truck is bone stock with 166000 miles.