I think we finally figured it out. The 2008 F150 Limite 5.4 w/ 4 sp 3.73 is doing better. We are now getting 11.2 MPG where before the mods we got 8 mpg.
Our TT is a Rockwood Sig Lt. 8315 curb wt. of 7200 lb ready to go 8050 lb. The changes I made are as follows.
Banks Ram Air system at $450.00 and ECM reprograming tool at $300.00. Reprogram to Heavy Tow... Before the mods the TV would struggle up the hill here in S. Calif. At home base we are 800 ft. elevation. On a trip before the mod to Idyllwild CA at 6500 ft. we had some hills we pulled at 30 mph and were lucky to get 6-8 mpg. After to mod we made our last trip to Yosemite National Park. Elvation to 5500 to 6000 ft. One grade called Priest Grade was 5 miles of 5-6% switch backs going into Groveland the TV did great pulling the hill at 45-55 mph. The entire round trip of 1100 miles the average was 11.2 MPG.
We had no over heat even with temps of 95 deg. The TV is a 2008 F150 Limited with tow pkg. trans cooler 22" tires and 3.73 axle. We use a Propride hitch and P3 brake controler.