Your profile says you have a throttle body spacer. If that's still on there, lose it. It could affect the tension on the throttle cable and they serve no purpose on the Zetecs/Duratecs anyway. Also, like Algorhythm said, the TB should have a screw with a spring on it that adjusts the idle RPM's.
The "idle" screw doesn't really adjust idle. It will for a day or so after you adjust the screw, but eventually the computer will "learn" that more air is getting past the TB than it was originally programmed for and will adjust timing and fuel to compensate. The only real way to adjust idle is with a tune. All that screw is for is to keep the TB open just a hair so the engine doesn't form a vaccum seal...if that screw isn't properly adjusted you'd have to really push on the pedal to get it to move after the engine has been sitting at idle for a short period of time.