Pro's and Con's of Mustang Handheld Tuning Devices:
The SF4 Strategy Tuner and the SCT LiveWire are handheld units with LCD displays that are used to flash, or overwrite, the existing tune on your car's computer. They hook up to your car's ODBII port located under the dash on the driver's side. They hold three total custom tunes.
The first time you use them they will download your car's stock tune into a 4th slot for safe keeping, so you can return your car back to stock at any time. The unit "VIN locks" to your car, so it can only be used in the first vehicle it was used in. They cannot be unlocked without first returning the original car back to the stock tune.
You will have the ability to edit certain parameters directly on the unit such as your air/fuel ratio, your final spark value, gear ratio, etc. which can be great for racers at the track and customer's with wide-band O2 sensors. New tunes can be emailed to you instead of having to send back the entire handheld tuner for reprogramming. Switching between tunes can take several minutes, so you are not able to switch on the fly.
Custom vs. Strategy Mustang Tuners:
A strategy tuner such as the Predator contains generic tunes designed for a fully stock car. They have a limited amount of user adjustability, but allows experienced users to help dial-in air/fuel ratioes, spark, etc. for mild bolt-on modifications and varying conditions. Some feature selections for common MAF and injector changes, but can run into complications due to subtle variances in the car's configuration.
A custom tuner or chip such as the Eliminator, X4 PowerFlash, or LiveWire allows the tuner complete adjustability of about 1000 to 3000 different variables (depending on the year/model) in the car's computer to accommodate for modified cars. This allows tunes to be created directly for a car's specific configuration, and it's the only way to tune heavily modified cars.
Handheld units such as the X4 PowerFlash, SF4 tuner, or the SCT LiveWire tuner allow you to make the same end-user adjustments as a strategy tuner in order to accommodate for varying track/weather conditions etc. However a handheld unit starts from a custom tune instead of the generic tune, so the end result is more precise.
Fitment includes: 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, GT, V6, Cobra, ShelbyGT500, Mach1, Bullitt, Boss, LX, SVO, EcoBoost, ShelbyGT350