Most of the folks I know start talking about bypassing cats when it comes time to replace them... due to the relative cost compared to the rest of the exhaust system. The cost of the cat is easily half of the price of a new exhaust The problem with cats and older cars, as indicated by some of the other responses, is that if you do not have optimum mixture, it will cause performance robbing backpressure Its nice to know that a well tuned modern motor can make 700 hp on cats, but I won't be putting them on my carbureted 454 vette any time soon
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