A test sequence was conducted on a General Motors prototype using a catalytic exhaust manifold system concept. Due to the consistent success displayed by this system in meeting the required 1976 emission level in the General Motors laboratory, an evaluation program was initiated. Beyond necessary engine modifications, a vehicle was equipped with four major emission controls: (1) A quick heat intake manifold, EFE, to assist in cold start fuel evaporation. (2) A Grace noble metal catalyst for oxidation of hydrocarbon and carbon monoxide. (3) A Gulf noble metal catalyst for reduction of oxides of nitrogen. (4) An air pump and associated valving to supply air for exhaust port oxidation and oxidizing air to the Grace catalyst bed. The GM prototype system was tested three times from a cold start using the 1975 Federal emission test procedure. It appears that this prototype system is an excellent candidate for extended mileage evaluation.