I would suggest to save up a little extra to get a handheld tuner instead. I have the Bama X4 tuner from AM, and so far I am happy with it. I have heard great things about Brenspeed and Steeda too. With the tuner you get way more bang for your buck, as you can correct the speedometer, ready and cleat any DTC's (check engine codes), adjust shift firmness (if automatic), and also get a few hp extra. Just about anyone who gets gears go with the tuner instead of a calibrator tool.
2003 Mustang GT
Intake & Exhaust: K&N FIPK CAI, Mac O/R H-Pipe, Custom Catback w/ Magnaflow Magnapack Mufflers.
Suspension: H&R Super Sport Springs, KONI STR.T Shocks & Struts, J&M Caster Camber Plates, Steeda Bumpsteer Kit, UPR Elite LCA's & UCA's.
Performance: BAMA 93R Custom Tune, FRPP 4.10 Gears w/ Terminator spec T-Lok.
Planned Mods: FLSFC, Eibach Sway Bars, Throttle Body, Plenum, Rims.