marko

as dusan correctly states, the best solution is to fit a kit such as the BMC CDA (any enclosed kit will work just as well) in place of the standard airbox and take a cold air feed from the front bumper. you will be best off removing the battery, battery tray and fuse box to gain access. you can run the cold air feed to behind the black plastic in the front grill but it will come out where the plastic has no holes (right on the edge) so the best solution is to drill some holes in this so it matches how the middle section is.

this is tried and tested and gives great results