Nissan Repair: does my car has 1 or 2 catalytic converters, dual exhaust pipes, dual exhaust system

Question
how can i know if my car has 1 or 2 cat converters ,also i heard that there are some illegal cat in California  is this true how can i know if aim buying a legal one?

Answer
Hi there,  a single exhaust system, one that is found in cars with line 4 or 6 cylinders, has 1 cat and usually 1 before and one aft oxygen sensors. A dual exhaust system that is found in V6 or V8 engines, must have 2 cats. A dual exhaust system, means that the exhaust pipes from the left and the right banks are NOT connected in any way and they operate individually. Dual exhaust pipes or pipes that are connected after the 2 exh. manifolds and they end in 2 pipes at the end of the car they are not considered as a dual system and they incorporate 1 CAT. So I recommend this: Take your car to a muffler shop, preferably an ASE certified one and ask them to lift the vehicle to determine what type of exh system it uses. Any reputable and certified muffler shop will not sell nor install illegal or modified catalytic converters in the state of California.