You will need a rivet gun, 3mm drill bit and drill, 5 rivets (3mm wide x 6.5mm head) and some sort of good glue or panel adhesive ie sikaflex or Tigerseal.
Removal of the air intake is detailed in the 'how to de-lip the air intake' Click Here.
If you are fitting a scoop you may as well de-lip at the same time.
Place the scoop over the air intake with the opening facing towards the front of the car (to the left), ensure the air intake is up the right way (it is labelled UP on the back of it).
Remove the foam rubber seal from the back.
Using a pencil mark the 5 holes that are to be drilled using the 3mm drill bit.
The Holes have now been drilled, check to make sure the rivets fit in each hole.
At this point you have a choice, you can leave the original centre cap in place
unmodified, leave the centre cap in place and drill a few holes in it or you can
do as I have done here and put mesh over the hole.
Using the panel adhesive (bonding agent) I placed a few blobs around the right
half of the mesh and the scoop edge.
Push each rivet in place and ensure the scoop is going to be fitted correctly.
Push the gun onto each rivet and pump the handle, the rivet will pull the scoop into place and will set itself by snapping the unused stalk off the front.
Once all 5 rivets are done, use a damp cloth to clean up any excess bonding agent/glue.
Refit the foam rubber seal and allow the adhesive to dry according to the instructions.
You have the option at this stage to paint the rivets with enamel paint if you wish.
Refit to the car and admire your handywork.
You could use self tapping screws instead of rivets but finding such thing with a nice decorative head proved to be harder than I thought, some people have managed to find allen key headed screws which look very good also.
You may find you will have to cut or trim the screws down if they interfere with the foam rubber seal or the Tridion when you refit the intake to the car.