Not really virgin but am to this truck and trailer. (I've towed a 20 something foot wells cargo with a 460cc Ford when I did roofing).  Anyway, here are my questions. I just picked up a 33' fifth wheel travel trailer. Dual axles, 8400lbs dry.  My truck. 98.5 24v with a bhaf and 4" straight pipe. 285/16 tires.  1. On the way home the truck had a hard time on hills. For example. Went from 65mph down to 45mph on a moderate grade hill. About a half mile long hill. Rpms were about 2800