A split heat recovery steam generator (HRSG) arrangement including a first HRSG coupled to a turbine and thereby receptive of a portion of the exhaust gases to deliver the portion of the exhaust gases to a compressor, a second HRSG coupled to the turbine and thereby receptive of a remaining portion of the exhaust gases, which includes an NOx catalyst and a CO catalyst sequentially disposed therein to remove NOx and CO from the exhaust gases and an air injection apparatus to inject air into the second HRSG between the NOx catalyst and the CO catalyst to facilitate CO consumption at the CO catalyst.