I have noticed as long as I can remember that when on the HWY if I step on the gas to accelerate my TB will drop down to 2 or 3rd gear and rev at about 4000 RPM. I dont know if this is normal, can others weigh in please. Does your vehicle have power in 4th gear ? I get about 19mpg on the hwy so it cant be anything too serious but Id like to know what other vehicles have for power so I can compare.