My 2006 Lexus gs300 throws a code p0505 idle air control system

What is your question?

It has erratic idle to it and often drops to 450 rpm, have not had it die on me or cause any problems. The Lexus dealer told me they cleaned the throttle body and the code keeps coming back and also told me he thinks my throttle body needs replaced possibly for a cost of around $1100. If i replace the throttle body myself will it screw the computer up and cause me more problems?

How long has your 2006 Lexus GS300 had this problem?

Few weeks