So I was towing a 28ft travel trailer roughly 6,500 pounds on the interstate going about 70mph. When I would start to climb a hill I felt like I was lugging the motor with my foot to the floor struggling to maintain my speed. My rpms we’re jumping up to 2500-3000. The truck is an 07.5 6.7L 4x4 Auto with a H&S XRT pro tune. I thought it would tow much better than this. Any ideas what’s wrong or what I should do differently? Thanks!