Regard your comment on how the burner is lower on the micro, I'm wondering if that's the possible cause of CO, would it be possible to unscrew the stem from a PR, cut some off, retap the thread and drill the air hole, and achieve the same thing? Would make the burner lower and easier to shield from wind too.
I don't know enough about adjusting the air/fuel and lack the equipment to drill it, so I can't try it.
You could do it, and it might or might not work. But why go through that when the professionals who have state-of-the art carbon dioxide monitors have done it for you?
Messing around with flammable gas burners isn't necessarily the best thing unless you really know what you're doing.
HJ