Some are better than others, FORTE is good as is MILLERS.
A lot depends on why the injectors are sluggish, these additives will NOT get rid of varnish and gum deposits from where a car may not have been used for months on end.
None of the additives even come close to ULTRASONIC cleaning though, but aren't ultrasonic money either, which is normally around £50/60 a set to clean, but you will know the CC/min rate of each one after as well.
tabetha