I highly doubt an 02 sensor can cause all of this. How is your gas mileage. Your gas mileage can tell you a lot about how your 02 sensors are performing. When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to. All in all check to make sure your car is tuned! You said you have an intake and TBE. Please make sure your car is professionally tuned. If its not, Your car will trigger all those CEL lights. Would you know if the previous owner put a tune on it? Because even though that year subaru can go awhile without a tune, with all those miles i would hope somewhere in that cars life its been tuned somehow. And that knocking sound you hear in the morning is pretty normal for a subaru with all those miles. Its Piston Slap. Car cannot handle much abuse without a rebuild.. Im telling you that much. Next step is Rod knock.. and a spun Bearing..