Good stuff

Just FYI, there is no "idle screw" on a fuel injected engine, on Fords its called an "anti-diesel screw", this screw also set the minimum voltage for TPS(throttle position sensor) which matters for best running

Proper way to adjust it is to warm engine up fully
Let it idle and open the hood
Unplug the IAC(idle air control) Valve, the 2 wire connector
RPMs should drop to about 500-600, engine barely running

If RPMs don't drop turn the anti-diesel screw counter clockwise and RPMs should go down
When engine is barely running its set
Plug back in IAC Valve and RPMs should go back up to about 750 on a 4cyl, 800 if automatic

The Computer controlled IAC valve is what should set the idle on all fuel injected engines, that screw should not effect idle at all, if it does then something else is wrong