xylene and percentage of MEK has no effect.
I was also told to lacquer thinner/ acetone, but this also has no effect.

However from time to time I do get some flakes to dislodge

I figure that since non of the above has worked that I am just using the wrong chemical,
and starting to think that if the ink caused the problem then should I just fill the head
with some fresh in and let it sit?

Also what I have not told is that I bought this machine and it sat for a year
with ink in the lines and heads.

All of the heads except the magenta have come back to life and improve with usage.
Someone was very kind to me and loaned me a printhead for the time being :)