I agree the 066 was smoked! The 660 (poor picture) looks almost like carbon scoring.
If you will notice in the 660 piston pic the top edge of the piston broke off and scored the side of the piston but did not harm the cylinder wall or exhaust port.
I am the only one who sharpens the chains and my foreman is the one that runs saws other than me so he gets his ass reamed for running a dull chain and he has a habit of changing chains before they get to the dull point because we are using such aggressive chains.
I pulled up on site as the saw started acting up so I saw the fuel that was left in the tank and it was a mix, the same mix was then ran for the rest of the day in the 290.
The 066 is now at the saw shop and with all the information that I was able to give it is suspected to have a bad electronic ignition module but he is tearing into it after pressure testing it and I'll get those results this evening.
Thanks for all of the input guys, I'm learning more than I expected already and that was my goal. I suspect that we are not watching the gas mix enough and the atmosphere down here has been rather dry the past few days so maybe a combination of that and running it so hard cutting firewood caused my latest problem.