I would be highly skeptical of the injector diagnosis. I have been a Hyundai dealer tech for 6 1/2 years, and can remember replacing maybe one, or two injectors on Hyundai's in that time period. Unless someone poured sulphuric acid in your gas tank, (or other contaminant) I doubt very much if your problem is the injectors. If you have the 1.6L eng, the common item to consider would be the 2-3 coil pack. Provided the info you presented is not skewed, I would change mechanics in a heart beat.
All the best,