Mass Air Flow Sensor problems of the 2003 Lexus RX300

I called my local Lexus three times prior to June, 2012 regarding lights suddenly illuminating on the dashboard. I had a recurring issue where the check engine and vsc warning lights would illuminate. Each time the customer service agent told me that the lights would go off when I refueled. Three times the lights did go off (after several days), but once I had to have the dealer reset them. The most recent occurrence resulted in the dealer telling me I needed the air fuel and air flow sensors replaced, a repair which cost over $750. 00. As an aside, every time I called to inquire about the lights being illuminated my car was under warranty and no repairs were suggested. After the warranty expired I was then advised that the sensors needed to be replaced.