The Focus and Mazda 3 are 90% silmilar, and many parts that work on a Focus work on the 3. The Focus is even available already with a low emissions version of the 2.3. Guys in the Focus world are already running mid-14s with N/A 2.3 cars (Just a CAI, Exhaust, pulley, and header will do it for you [but of course the Focus is lighter than the Mazda3]). Check out these sites, and look at the PZEV (the low emissions version of the 2.3) and Duratec (Ford's name for the its new line of 4cyls) tuning sections:
http://www.focaljet.com/ubbthreads/ubbthreads.php
http://www.focusfanatics.com/forum/
http://www.focaljet.com/ubbthreads/ubbthreads.php
http://www.focusfanatics.com/forum/