i just bought my first subaru and i bought a fixer upper i am a pretty good mech but im stumped. when i bought my 2003 wrx it sounded like an air raid seiren and had no power. i pulled down pipe off to check if cat was plugged and it still ran the same. but i felt turbine on turbo and it was bad. so i replaced turbo and car still wont rev fast . and exhast before cat glows red. and code po031 i have not even driven it cuz im afraid ill damage new turbo . 16g turbo was put on it and its all stock

 

Replace the Up-pipe. That was what probably destroyed the turbo in the first place.

 

The po031 code is the front O2 sensor in the manifold collector which is the only really important O2 sensor in regards to how the car will run, so I would think about replacing that. Also when you say the "exhaust before the cat" do you mean the cat in the uppipe or the cats in the downpipe. But like Strider said, I would get rid of the factory catted uppipe and either go with an STi unit or an aftermarket one.

Thanks,
Rick