when i bought my accord the previous owner installed a street illegal catalytic converter that caused the car to fail smog tests

my fuel is burnin very rich, i had the car on in my garage and it smelled like gasoline very bad..could this be the catalytci converter? i have the stock one i was thinkin about puttin it back on

im also only getting like 17-20 mpg city, and i drive it very conservatively..the car also has an exhaust sysstem and intake and i thoght this would increase the mileage?

i really dont kno what is exactly wrong but im guessin its the custom converter...does any one have any suggestions_

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