Hi mate,
you could make a separate cold air intake but i haven't..
what i have done is remove the airbox, clean it out...then drill some holes in the wing side and front side of the bottom half of the airbox - you don't want to drill holes on the engine side as that is likely to let in hot air which is not good for induction..
Also remove the plastic internal intake pipe coming in from the air feed...mine wouldn't come out even when i pushed the retaining pins in...so i broke it off...
Not sure about performance gains but u'll get much better sound..