Here's where we are on this repair - new air filter to replace the K&N, the OBD II diagnostics - Volvo specific - indicated Mass Air Sensor, the generic OBDII indicated P0172, O2 sensor. The forward O2 sensor was replaced, engine light came back, same error code, the Mass Air Sensor was replaced this last week, CEL came back on the same day. I'm not sure what the code is, and won't know until tomorrow when the car goes back to the mechanic that did the Mass Air Sensor. Oh, and yes, the CEL has been reset between each of these steps, so it's not just "still on". I have looked (visual inspection) of all my vacuum lines, and replaced three of the little rubber elbows - the one nearest the turbo was dry rotting. So possibilities?

I was also wondering what kind of around-town fuel mileage people are seeing with s70 GLT's - I calculated mine today - 18.2 mpg, which seems low. Not sure of highway, I don't travel that way often.