I was going to say the air filter but you have an aftermarket kit. Could be the gears and is the tranny stock? Stock tranny w/ a lift and 38 tires does not mix when towing.You might want to figure out what chip is on it and see if it is recommended for towing. If it is the tranny an you want to get a new, better one I would recommend Brians Truck Shop, its in Lead Hill, Arkansas. Hope this helped and good luck w/ your truck!!
Ohh yea
