------NeeD Help------
A stuck open idle air control valve, or one that won't fully close, is not unmetered air I don't think and the computer knows what position its in so everything will run fine with the exception of the high idle.
also check the cabling going to the throttle body, it's unlikely but the the throttle plate may not be closing all the way either. those are the only two things i can think of to cause the condition you describe, and still have the engine run well and not throw a code.

