How to reduce Idling speed on corolla 08 automatic?

Hello, mine is idling at 800rpm when fully warmed with ac,heater,music,lights Off.
i beleive the ldling should be 600-800. i am thinking to decrease to 600 to save fuel. even on stop sign, red light, it idle at 800, i think 200rpm are pretty enough to burn more fuel so that's why i think to reduce to minimum where it should not stall.
i have clean the throttle body, air filter, and mass air flow sensor with correct equipement. i also used 91 octane with almost empety tank but still not any change to idling.
we had also Ford freestar 2005 V6 and it idle at 600rpm with 6 cylinder so i beleive if a big van like this idle at 600 than why not a 4 cylinders at 600.