PO325 means the sensor is toast. I tried the same thing with the Forester, clearing the code only to return. Replaced the sensor, problem solved.
It is located near/under the throttle body on top of the motor. If you search you should be able to find a pic. Easy install, just don't tighten the bolt too much on the new one, the specs are light (around 10-11 lbs. I think) and you will smash the sensitive plate... You will also need a socket extension to reach it.