ever since i replaced my 130K old air filter with a K&N filter my car has been getting a check engine light. I detach my batery, and mabye a month later it comes back on..but now it came only two days after i detached the batery so i figured something must be wrong, even though the car runs A-ok. I made an appointment with the local MB stealership, and they told me that it could be bad spark plugs( which i told them that its not) or that there is a possability that its a bad Mass sensor(which im fearing is not)...Im gonna drop by tomorow so that they can check the car out...but my question is, if its the mass sensor, how much do you expect that to be ($$)

Elvir