ZX2 cams are a downgrade vs stock Focus ones.
I'm woth those who say to pull the head and deck it. But unlike Tom I'd shave a lot more. Just be sure the cooling system is able to handle the extra heat; oil cooler is a very good investment here.
I'll second the 5 angle valve job and cams, though I'd go stg. II or better being you're running a higher rev range than a street car.
Gears also help by multiplying the power you do have. Just the same as reducing tire circumfrence does (the added benifit of smaller tire can also be less wieght).
Don't "think outside the box".
There is no box.
Do it correct, or do it twice.