Sorry for not getting back to you sooner, somehow your last message got lost in my email...
Power clean cycles don't move much ink thru the lines with the 7890/9890 and 7900/9900 printers, compared to previous models. For example, with the 7880/9880 and 7800/9800 2-3 power clean cycles is enough to move ink from cartridges to the print head, but you would have to do dozens with the newer models to move ink the same distance (so, power clean cycles are less powerful with the newer models).
What is your current status- is your output back to normal, or are you still struggling with dark output?
Please let me know, thanks and best regards~ Dana