CECO burner on old American 13B boiler

l recently had the opportunity to try to address the combustion tuning on an old American hot water boiler. It has a Combustion Equipment Company burner with up to 12 orifices at 3/16" each. That puts the firing rate at over 1 mil btu. With there being just 7 orifices being fed, and I'm not quite sure how that works, the boiler still fires at 600,000. The burner model is B12-X. I can find no information on the burner and need manifold pressure to have the best chance of not condemning this unit immediately. CO levels are high, but the main regulator is wonky and I want to replace it, but don't want to spend too much time on it if I have little chance of winning. Anybody have any experience with these burners and have some data?