morning all, drilling your air box is very simple, i've been fiddling around with polo's for years before i got my cupra infact i've still got a mk2 coupe S a mk3 G40 and a mk4 1.4 runabout but they are all running veritions of the same engine you have. anyway for drilling the box just get a 20-25 mm hole saw and wack as many holes in the ''dirty'' side of the filter box as you can get in it, anywhere that looks big and flat enough to put a hole in drill it! also with regards to induction kit's i can recommend anything from green cotton as they have all worked for me, and also why go to halfruds and get ripped off when there are lot's of traders on the forum and most of them deal with all the majore airfilter manufactures, so they should be able to offer you a much better price, i know bill at badger 5 can supply most types of green filter, so he may be worth a look. and one last thing with exhausts, a de-cat and straight through centre section will give you a nice sound, but dont be tempted to in big on the bore, because you dont need it and it will just sound crap, a fully sorted G40 only need's a 2-2 1/2 inch system at most, i did run a group N rally side exit system on my mk4 and it was only mm's bigger than the standard system, but the gain was good from it and the sound was nice although it had no cat and very limited silencers so the law were not to fond of it! anyway hope that helps a bit.