Hi, I have a 98 S70 glt and have a check engine message P0172 for rich mixture. It was originally associated with an O2 sensor low voltage message too. I have replaced the O2 sensor and now I still have the P0172 message. I've had a shop look at it and they checked all of the vacuum hoses and they think that it is the fuel regulator or damper. Though it could also possibly be the Mass Airflow Sensor or maybe even the fuel injectors. I think that most likely it is the fuel regulator or damper though, do you have any ideas on how to check these or should I just simply start with the regulator and see if replacing that works? Thanks