Technically, all the 3rd gens are "fly by wire". The cable on the earlier 3rd gen trucks simply connects to an actuator on a hall-effect (or potentiometer on very early 2003 trucks) device. That signal, which is purely electrical, is fed to the ECM, which then determines the demand fuel flow.
It is "throttle by wire" in that there is no mechanical connection between the fuel flow rate and the throttle pedal.
-Ryan