Manifold/header/muffler/tail Pipe problems of the 2010 Toyota Sequoia

Discovered rear bumper was severely burned around tail pipe after pulling a trailer. I purchased the vehicle new from modesto Toyota. I brought the vehicle to modesto Toyota and reported the problem as a factory defect. They inspected the problem and reported back to me that there was nothing wrong with the tail pipe and because it was beyond the warranty period there was nothing they would. I have looked at another 2010 Sequoia which pulls a travel trailer and discovered the same problem. I feel this problem has a potential to start a fire and should be covered by Toyota regardless of vehicle miles.