Pedal Commander Throttle Response Controller?
#3
I wouldn't mess with that thing, it's almost as much as a tune and a tune will take care of the lag and give you other benefits especially if you have an auto. If you get the tunes for life, you will get a new tune to maximize your gains from any mods you plan or might do in the future.
#4
If your worried about voiding your warranty with a tune it 'might' work. I have read a lot of good reviews (pedal commander) on the thing your looking at. Several people on another Mustang Forum I'm on, love the way it works. My tunes took care of my dead throttle response.