bought a 07 sporttrac v8 4x4, for towing a camper, got 9-10mpg on tow, i was getting 15mpg on stock tires, no/tow, commuting, bought new tires (yokahomas) and a K-n-N air filter- now getting almost 17mpg. but after having it for 4yrs, my tranny is starting to do some odd things, like pausing on...