I recently replaced the mass air flow sensor in my wife's 2000 RX300-All Wheel Drive. Reason for replacement - I damaged the sensor while trying to clean the two sensing wires. The Toyota/Lexus part number for this sensor is 22204-07010. My local Lexus dealer wanted $195 for it. My local Toyota dealer wanted $158. However, I found a remanufactured Toyota 22204-07010 at Autozone for $79.99 plus tax after giving them the core (core charge was 65.00). Note: this is the same sensor used in the 2001-2003 Toyota Highlander with V6 engine.
To Install...I disconnected the battery to cancel any codes that were set (check engine light was on), reconnected the battery, put the part in place, tightened the two screws and reconnected the wiring harness to the part.
Her car is, again, purring like a kitten. :) Location - Long Beach, CA