I figured.. That is a bit low.

Maybe this has been discussed in another topic, but I wonder if it's the cat that's killing your mileage, or if it's a poor-running engine that's killing your cat?

Cats usually fail 2 ways

1. Get clogged, something is wrong with your motor.

2. Get broken, they can crack with age, or if you hit the cat with a big dip or curb or something.

now you's are starting to scare me... what could be wrong with my motor that could have killed my catco.. and i started to notice the smell of a bad catco before i changed my o2 sensor..............
...

Running rich will kill a cat in short order. It looks like you've rectified that problem.