you dont have to get a piggyback there are FAR better ways to tune... I would highly recommend you fork over the extra bucks to get it professionally tuned by someone who KNOWS the v6 mustang
... there are only a handful of course. Alberto is very good, there are others all around the us so see who all is where. Check the sponsors page.
Alberto can get you a mail order chip that will get you VERY close you wouldnt belive, and by mail order i dont mean just a off the shelf, he will do a great custom job on it for you, he will just send it to you though the mail. (americanmotorsports.com) you can then get a tune and get your A/F checked and confirm the specs to make sure you are where you need to be