No matter what, I would never ever go piggy-back.
The purpose of a PB is to keep the factory ECU doing all the gauges, lights OBD2 stuff and non-major engine controls.
Well IMO, if you're to the point where you need a tune that bad, then man up and go standalone. It's not much more money and it'll open plenty doors the PB can't.
I found this rather quickly --> http://tunertools.com/proddetail.asp?prod=HYP-62003
No clue on how well it works.
Also I'm kinda curious if the Focus duratec stuff could tune an early 3?