An Injection Service consists of an aerosol or shop air introduced solvent directly into the fuel rail after disabling the car's fuel supply so that the car runs only off the solvent until depleted. This service is not so much for the injectors as ridding the combustion chamber of carbon buildup. There also is a service in which solvent is srayed into the intake manifold(s) to rid them of carbon deposits (from intake flow reversion). It usually costs around $69.95 in this area just for the injection service.
If you are concerned with only the injectors themselves, you can have them flow tested and calibrated on the bench or bite the bullet and go up one size (19lbs. to 22lbs.) cheaply with injectors from a supplier such as ACCEL.