Im in the same boat too. cel just came on a with p0420. I looked around for a cat and I found a catco brand cat for 310 shipped OE subaru for 530. But before buying a cat I monitored the 02 sensor the response is slow. I replaced the front last saturday and cleared the code. I have to drive it more to complete a drive cycle so that the OBd2 system will be ready. If the cel comes back on I will scan it again and if its the same code then I will replace the cat. Oh by the way the 02 sensor is OE an is 80. I have a 02 rs. will update. When your cel went on did the car lose power and burn rich? Mine did so I was wondering maybe if my cat is clogged.

 

Yeah, the knock sensor wasn't cheap but at least the light is off.

My cat was definitely clogged. Sometimes during accelerating, and almost always going up hill the car's power would jam. It felt restricted. After the cat was replaced, this thing never stutters just hums like a bee and revs forever. It's great to have it back.

 

Why are you pissed at your cat? Did it **** in your car?