The report discusses NOx emissions, at an existing coal-firing utility boiler, that have been controlled by modifying normal combustion parameters using the boiler's normal operating control system (without adding new hardware). The combustion modifications (CMs) studied included unusual fuel/air ratios at selected burner elevations (staged combustion) and decreased excess air flow rates. Side effects of the new operating conditions were also studied, including: changes in boiler efficiency, other emissions, and (for the first time) detailed studies of boiler tubewall corrosion rates.