Ox formation is a function of flame temperature; reduce the flame temperature and the formation of NOx is reduced.
CO is or can be burned, so reducing flame temperature has somewhat the opposite effect on CO.
Water injection for NOx reduction is used to cool the combustion flame temperature to reduce the formation of NOx (nitric oxide). It's injected directly into the combustors of most GE-design heavy duty gas turbines, and on a rare few is mixed with liquid fuel before being introduced into the combustor(s).