A friend of mine had his cat. convertor plug up very very badly so he took it off and knocked everything out of the inside of it. With nothing inside the cat. will this affect the rear O2 sensor or does it need to be replaced with a dummy?

 

I will need to be replaced with an oxygen sensor simulator.

He can get one here: www.thefastman.com

 

what he said! ^^^^

It will probably throw a CEL without one.