I installed a air ducting via the fog light some time ago. I used some90mm black metal wound ducting from ebay, which was quite reasonably priced. The only probalem ive found with that ducting is the fact the copper(?) wound inside the duct has gone a bit rusty so im thinking of spraying it or something inside.
Basically I have modified the fog light grill by adding a fibre glass shroud behind the hole, as there was nothing for the ducting to connect to on the back of the fog light grill. it seems to work well although I have no idea if it makes a diffeence to airflow or not.
There is a nice big hole perfect for 90mm dutcing just below where the air filter sits so its quiet convenient.
Not had a
problem with water ingress as the filter is still pretty clean, where as when I had thr air filter located behind the fog light grill it got into a right state
The fog lights option can be easily turned off in vag-com.