Been looking at the 2017 TRD Pro . My current TRD Off road has 4.0 engine and the new TRD pro has a 3.5 engine . Why did they change the engine ? Is it better than my 4.0 (Gas mileage,horsepower,torque) ? With my current Truck,guess what, I haven't had any problems,and it takes me wherever I want to go.I have 88,000 on it and figure maybe I can get great trade in value ? Is this TRD pro overkill ,how does it ride on the street ?