If we’re being realistic, a Ford Focus SE turbo kit probably isn’t worth the money or effort you put into installing it, as the performance improvements aren’t all that spectacular. In terms of cost effectiveness, you’d be better off selling the SE and buying a Focus SV or SVT, as both provide a much better base for turbocharging or modding.
Of course, if you’re dead-set on improving your Ford Focus SE, there are other ways besides adding a turbocharger—you might look into engine tuning, an upgraded suspension, bigger wheels, etc.