what is a fly-by-wire throttle?
I could be wrong but I think this refers to a throttle system that's actually controlled by a computer. A Standard acclerator pedal is mechanically linked to the throttle and therefore when you push the pedal, you physically control the throttle. A "drive-by-wire" or "fly-by-wire" system is when you press the pedal, the only thing that does is send a signal to the computer which actually operates the throttle based on the pedal and a bunch of other factors. There's several advantages and disadvantages to it. The advantages are that the feel can be adjusted much easier since it is not dependent on the actual throttle arm. Another advantage is that the throttle response can be adjusted on-the-fly based on the current needs and driving style. You know how the Impreza has a problem with the throttle/pedal bouncing around on rough roads. Well the computer could eliminate this phenomenon almost entirely be sensing the roughness of the road and determining what it thinks you're trying to set the throttle to. The big disadvantage and what scares most people is that they don't want their vehicle speed controlled by the computer. Most of us grew up in a time when automobile computer failure was so common that we'd sit around and drink beer and talk about the "good ol' days" when there were no computers. We've heard stories about cruise controls failing and causing the throttle to stick and accelerating people to 120 mph to their death. I had it happen to me once in my '86 Mustang. not a very good feeling.
The term originated from the new jet control systems that have very few mechanical links to the pilot. Most of the pilots controls are linked to a computer which actually flies the plane. The pilot really just tells the computer where he wants to go, how fast he wants to fly, the altitude, etc. and the computer does the flying.
If I'm not mistaken the current Porsche 911 has a drive-by-wire throttle setup.