I'm inclined to give something like that system a try. For that price you can't go wrong, even if it's just to be a guinea pig to let the rest of the forum know not to use it! lol
As far as I understand, on 03-04 1/2 it would not throw a CEL
code. However, if Ford updated your programming after a certain point (I don't know when this was) it is possible even an 03-04 1/2 WILL throw a code. Only way to know for sure is to try it and find out I guess.