suspension wise your right on with Eibach. they are very good and highly recomended for the focus. i have heard of peopleusing the Eibach springs with some adjustable (not in ride hieght but stifness) shocks but cant remember what they are called.

you could just do the springs or you could get the complete kit with the dampers as well. its up to you realy.

as for induction i would never get an open air kit as this sucks in all the warm air from your engine bay and can hinder performance as well as hurting your engine!!! you could go for a Pipercross Viper induction kit but its expensive. a lot of people have used a K&N replacement element (panel filter) along with a st170 intake pipe (goes to the airbox) as its bigger than standard ones. you may need the bottom half of the air box from an st as well, i've not done this (my car is standard) so dont know what problems people have encountered, and also you can fit an air deflector out of the st (this is the plastic piece which your intake sits on). all this is very easy and cheap and all i have heard is good reports from it. slight power gains and improved economy.