Very nice project, indeed.
I guess there will also be some engine tuning involved.
On my 4/4 Sport (2009) I removed the air filter box in front of the engine and installed a K&N open air filter system ( K&N kit nr 57-0686 for Ford Focus II ) directly to the air inlet at the rear of the engine via an elbow duct together with a funnel just below the radiator and an air ducting pipe.
This save some weight and gives a nice induction and exhaust sound.
D'herde Bart