Believe it or not at this point in your build, if its a manual tranny, you should consider an aluminum flywheel.
The Focus has a heavy flywheel that robs horsepower. An aluminum flywheel will reduce the rotating mass weight and improve acceleration.
Change your clutch while your at it.
After the head and some cams and gears you can get serious and think about individual throttle bodies.
But then you need a real dyno tune.