Does a Honda civic 2000 waste more has without a catalytic converter?

I have a Honda civic 2000 without a cat and has a pipe instead, it needs the secondary oxygen sensor. But I was wondering if the catalytic converter affects the gas usage an anyway?

Removing the catalytic converter reduces the back pressure which increases the air and fuel flow which increases the horsepower which increases the pollution to the atmophere

Repsect to Eshu, but that's not correct!

back pressure is only in play at max rpms. And at max rpms, that actually helps scavenge gasses resulting in better performance and more efficiant (not neccessarily better mpg's) buring.

and the o2 sensor after the cat does not effect mpg's or performce. It's only there for last output/final emissions sensing.

by 2000 cats were non restrictive anyway. The bb or baffle type cats are long gone.

^let me make it simpler than these guys. Removing your cat and/or muffler does reduce gas mileage and I know because I have a straight piped civic

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