I have an 04 rx8 and i was driving a few weeks ago and it just started bogging and had no power and was smoking so i turned around to go back home and it went away for a minute and then came back.When i turn the car on it runs fine bu when it get to operating temp it falls on its face and sounds like a harley. i took the car to mazda and they told me it was the cat, o2 sensor. i just took the cat out and put a new sensor in and cleaned the plugs but still does the same thing( only one cat right?). any help would be great, im pulling my hair out.

 

Go back and get the new CAT from Mazda.

It's free up to 80k miles no matter who owns the car.