1974 to 1979 GMC Pickup Truck Dual Exhaust System Illegal

My exhaust system is on a 1979 GMC heavy half pickup with a 350 engine. The exhaust consists of stock manifolds to a crossover tube with a dual exhaust with a catalytic converter on each side of the exhaust with a muffler also on each side of the exhaust, going to exit tubes just before the rear tires, why would that be illegal in California?


Answer:		California considers any emission system modification as an Emissions Tamper, even if the modification improves emission results. According to the Motor Emissions Application Guide your GMC requires only a single OC type Catalytic Converter. A modification adding a second CAT to the exhaust system will cause a smog check visual failure. posted by SmogTips Support

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