Be very careful about putting HID's into your fogs.
Remember that the reflector and lens are designed to create a focused beam starting with the light pattern from the halogen filament, not from the xenon arc. I got a set of higher wattage, tinted halogens that matched (well, closely enough) the 5000K HID's I put into the dipped and full beams on my 166. That way, the bulbs all look a very similar colour and the fog lights don't produce a wildly scattered pattern that will reflect back blind me if I use them in fog.
The dipped heads on the 166 are projectors so the beam remains fairly tight with HID's installed, but the fulls are reflectors and the HID's throw light everywhere (which when you're driving on an unlit road is great, but I'm now getting oncoming drivers flashing me from a long way away). I wouldn't want that amount of scatter coming back at me from the fog.