The design characteristics of the Wilford Smog Suppressor provided an opportunity to evaluate the effects of applying back pressure to the exhaust system and its relationship to reduced emissions. The testing was required as part of an evaluation of retro-fit devices to aid in reducing emissions in used cars. The device was mounted on a 1963 Ford Galaxie test bed, with a 289 cu. in. engine and automatic transmission. The device was tested under the 1970 Federal test procedure as stated in the Federal Register, Vol. 33, No. 108, Part II. Because of the increase of unburned hydrocarbons during the cold cycle and the lack of any meaningful reduction in both CO and NO, it appears that the Wilford Smog Suppressor has no beneficial effect on emissions.