Front O2 sensor replaced less than 1k miles ago. It was throwing codes for that. No more codes, and running condition improved after the change.
Mine: 2008 Saab 9-3 Aero SportCombi XWD: 84k, Black, MANUAL
Gone: 2002 SVT, #1654
Hers: 2010 Focus SES: 73k, Ebony, Auto, Moon and Tune