The ECU in your Ford Focus ST has locked within it huge potential for more power and performance. Unlock this power with a new ECU calibration from COBB Tuning or SCT Performance. Each of the aforementioned companies offers a handheld tuner that comes pre-loaded with OTS tunes. Furthermore, these devices offer you the ability to data-log, store custom tunes and clear DTC codes. Finally, this is the first modification that we recommend for your car, as it will be foundation for future mods.