The cleaners will only clean from the injectors and downstream. The TB needs attention considering your milage. In my experience fords in particular seem to gunk up more than some other brands. You don't need to take it off.. just use some TB cleaner and a toothbrush. It'll all emulsify and run out doing it that way.
btw, I did'nt mean to leave the impression that a TB would cause it. I don't think it would. More than likely it's carbon buildup in the combustion chamber.
btw2, Pull at least one plug wire and just make sure it's still torqued properly. I've seen them come loose if only snugged or if done when the motor was hot. Hot motor torque retention vs cold motor is not the same.