those rev knobs are pretty useful, although ive only ever noticed them in my old landcruiser bundera (1985)... i never noticed it in any newer cars (ie- not in my parents 100 series landcruiser, or my 1zz). am i wrong on that? does the 1zz/2zz have these knobs? I don't believe the idle speed can be controlled at all - set in the EMU. High idel could be as a result of another fault such as vacuum loss somewhere. Best to take the car back to the dealer!