Is there any way EFILive can be used to check things like return rate and other parameters to determine how healthy injectors are?

yep turn on pids balancing fuel flow rate cylinders 1-8

what should i look for?

i think between +/- 4 when motor is up to operating temp so you may want to log ect as well.....only works when idling as soon as you come up from idle they go to 0