Hello Kev,
firts of all i would like to congratulate you for all your work and knowlodge on xt 660 R!!!

I have a xt660R from 2010. I live in Azores (portugal - in the middle of Atlantic ocean).

My CO value is 21. I still have surging. Do you think i should increase that value? Or decrease? what is your opinion?

I do not have any mod or change. It's fully original.

Cheers
Luis Pedro Cabral