[flyingdeloreanmc]

I have a 2011 Forester X that I just bought and it was down about 80% power with a P0420 code. What I noticed is that this vehicle has two catalytic converters and when I bought the car I was told it need both cats replaced. Being a mechanic myself, I removed the rear cat, 3 bolts in front and 2 spring bolts in the rear, and then I drove the Forester around. It was LOUD but the vehicle drove as it should. I noticed the front cat was blown out and the rear one clogged not allowing the exhaust to get out causing the car to stumble, lack power, and feel generally lazy. If you have the skill to remove the oxygen sensor, you can enough skill to remove the rear cat and see if the car is restored.

 

[flyingdeloreanmc]

I forgot to add you could remove the oxygen sensor after the catalytic converter and then drive it to see if it has gotten any better. If it did, then the front one is fine and the rear is clogged. I did the cats on mine, and they are really very easy to change.