Or at least, how I moded mine.
Step one - Go to halfords and buy
Two 40mm diameter alluminium ducting tubes and one 45mm (about 500mm long each when streched, be careful to remove the glue without damaging the pipe)
Some two part bond that can span gaps
Some alluminium foil sticky tape
Step two - Cut off about two inches of the 45mm tubing (having streched it out first) with a sharp knife. Cut a hole in your airbox in the bottom, front, left hand corner as you look into the engine bay (so that the pipe can lead down behind the light). You should now have two air feeds at the front of the box, one on either side (one being the manufactures feed).
Step three - Cut another two inche section of 45mm. Remove the front bumber and the drivers side head light. Now screw the two 45mm pieces onto either end of one of the 40mm sections (they will go if fully extended but make sure you don't pull so hard it comes apart). Next screw the other 40mm section into the other end of one of the 45mm sections. You now have one long pipe with a 45mm chunk on one end.
Step four - cut yet another two inche section of 45mm and cut four or more slots in one end so that you can fan the ends over to produce a cone. Use the foil tape to span the gaps and create a cone to ram the air into the pipe. Then screw that onto the remaining 40mm end.
Step five - route the piping so that the cone will sit just behind the lower vent on the bumper and the other end it sticking into the airbox by about half an inche (any more and you'll be butting the panel filter). The 40mm tubing will fit under the light if you put it in the right place, so just move it about abit if the light won't fit in.
Step six - Once you're happy with the possitioning you have two choices; first one is to glue the 45mm two inche into the air box using the two part bond, then once it is set, screw the 40mm section into it; the other option is to buy a cuboid shaped sponge, chop off a strip along it's length about 15mm thick, make the hole in the air box slightly bigger, wrap the sponge round the outside of the 45mm end and force it into the hole, using the sponge to fill all the gaps and hold it in place.
You can use the foil tape to seal the joins between the 40mm and 45mm tubing.
Step seven - Re-assemble the car with the new air feed in place (using which ever holding method you prefer, I used the sponge until I was happy with it and have now glued mine in) and makesure your feed cone faces into wind.
Step eight - Face car into wind, start ignition and drive to rolling road for a test run.