idle speed adjustment

i tried to adjust my idling speed rpm from
1k to 5s-fe specification(700-750rpm)
first the idle screw was already kinda turned to the max
i just manage to turn some more with little bit of force
to the max, the lowest it gotten was 950

HELP!!!! What can i do to get my idle speed down to normal
700-750 rpm
-----------------UPDATE--------------------------
Sad to say, i thought it was just the ECU going wack...
so i reset it...(unplugging the negative from the battery for 1 hour)
and i start it back up....
First rev (from a cold start) went over 2k...and held it there for 1 1/2 second then
it drops dramatically down probably near 1 or below and rev back up


????
no idea why it does that..
????
2nd try from a cold start it dosn't the same thing again..

All N All
this hasn't cure the problem instead of dealing with 1k idle speed
i'm at 1.2k idle speed

i'm about to replace the fuel filter...
thikning about taking the intake manifold out and scrub that thing til i hear echos in them....ORRRR
replace the ignition wires which i think was the start of the problems i have(*poor mpg@20 or below avg)

ude sit there and let irt worm up for a good 20 minuts and see what the idel sped is, when you start a celica it idles at 1500 so it warms up the motor