no need to drill the airbox (i know this works on the g60 and most n/a airboxes - not 100% sure what the 16v airboxes are like) there is this cone piece that is at the front of the airbox (it is a air inlet) that fits right up to the back of the headlight, you can remove the piece from the airbox (it should slide right out - may require a bit of force) then you can remove the plastic piece that mounts behind the headlight by removing a screw or two. once you do that, i reccomend getting a k&n drop in filter. that should only be $35 or so for the new airfilter and under an hour of labor.
now with all of the money you have left, get an exhaust system (i dont know if you guys are required to run a catalytic converter over there) if you are, get a high flow cat. and a cat back exhaust system. if you are not required to use one, get a straight pipe and the cat back exhaust system. that should be around $200-$375 for that. doing exhast stuff is easy and it doesnt take long to do like putting in cams would.
use the rest and get a good tune up from a shop, it always helps to have a nice tune up from a shop. or if you want you could get a diagnostics of your car to let you know the wear and tear on the car for future reference.
hope i could help.
