My check engine light came on and engine running louder than usual, what is it?

What is your question?

My check engine light comes on often and then usually goes off on its own because I need a new catalytic converter but since it's over 14 years old it's not necessary repair. But now the engine seems to be running very loudly and especially when I accelerate. I had a whole new system put in 17 months ago, so I don't think that it's that it's a different sound