I know that I have read a lot of posts where people have tried cleaning the Mass Air Sensor with no luck. The last time I had a Mass Air code on my '96 C280, I did the following based on information from a friend that used to manufacture the Mass Air Sensor. First, used the CRC cleaner, then used contact cleaner on the connector, finally di-electric grease on the connection. It has been over nine months since the CEL came on.