I drive a 2007 F-150 KR and pull a 2020 GeoPro Travel Trailer, weighing less than 4000lbs. Without a load the truck is a dog anyway. Literally can floor the truck while merging and get very little accel. WITH the TT in tow, the truck is even worse, struggling up hills, getting 11-12 mpg, really just unacceptable performance for a truck that is supposed to have 300hp and tow cap of 10k lbs. What could be wrong? I would love to hear from the experts. The truck has 120k miles. I am the second owner. Otherwise it is in pretty good shape.

 

Get your cats checked for excessive backpressure and your intake air box checked for restrictions - I've heard of loose insulation in the fender well blocking the snorkel. Make sure it's got some fairly recent spark plugs in it.