Abstract: Emissions are controlled in a recuperated gas turbine engine using an apparatus and/or method. A fixed boundary recuperator comprises a gas inlet through which flows a gas and a gas outlet in communication with the gas inlet. An air inlet flows an air through the recuperator so that the air is in heat exchange relationship with the gas. An air outlet is in communication with the air inlet. A catalyst is disposed at least at one of a plurality of locations, with the locations selected from the group that includes a position immediately upstream of the recuperator heat exchange core, a position within the recuperator heat exchange core, and a position immediately downstream of the recuperator heat exchange core. At least one parameter of the engine is tuned based on desired NOx emissions and remaining undesired emissions are catalyzed in or immediately adjacent a recuperator.