Originally Posted by Tizzles
Its a high flow cat thats direct fit... i.e should just bolt in
No, it's not. It's an OEM style replacement. No sense in the OP buying it, unless the factory cat is clogged.
I had a single high flow in my old WRX, it was an improvement over the 2 factory ones (uppipe cat was removed before I bought it), did set off a P0420 without tricking the rear O2 sensor though. Dunno if it would do the same replacing just one cat, rather than 3. You can buy one cheaper than that Magnaflow too.