Here are links to sites that show you how to clean your throttle body and IAC valve. Yes, you will get better mileage..

http://www.yotatech.com/f2/cleaning-iacv-121097/

http://www.yotatech.com/f123/re-3-4l...iac-pics-92286

http://us.lexusownersclub.com/forums...howtopic=30723

http://www.examiner.com/examiner/x-4824-Tampa-Sports-Car-Examiner~y2009m4d17-Replace-clean-and-diagnose-idle-air-control-valve-IACV


Cleaning the IACV like this will save you roughly $500 at any dealership.