here are my opinions on this...
I work for a firm that represents one of if not the premier automotive lighting manufacturer in the world. over the years i've heard it all and formed some opinions and ideas that i feel are pretty strong. first and foremost, the best thing to do in a halogen housing is to use a non-hid setup for many reasons, but mostly it's for light management and glare reduction. however, i know a warning against using hid will go in and out many of your ears, so i'll move on.
for 9006, such as that in the ms3 fogs, the brightest, whitest and safest bulb you can get is a 9012 HIR bulb from toshiba (available from the great people at
www.rallylights.com). a 9012 is basically a 9006 with one tab too wide that needs to be trimmed for perfect fitment. notice i mentioned white light; while colors that lean toward the low temp yellow/amber region are generally considered superior for 'low light' and cutting through weather, the game changes when you compare a brighter bulb of slightly higher temperature to a lower wattage amber bulb. that is why the old Hella yellowstars in the crazy wattages used to be SOOO incredible, because they were crazy wattage, super bright and so intensely yellow, but they burned harnesses and posed a great danger to the greenies in Europe, so they are now a thing of the past. anyway, the reason i prefer the HIR because the white is just so intense while not stressing wiring (because the wattages are reasonable), and on a side note they do not leave a blue hue in the reflector/housing when the light is off like most of the high performance white light bulbs out there.
so it's my opinion that an HIR bulbs in the fog, with laminex film for protection and hue would be ideal. if you used yellow film you are essentially recreating the light that the awesome "old" hella yellowstars made- super bright and very yellow.
additionally, HIR bulbs are available for 9011 (9005) fitment, so those with GT's can enjoy wonderfully white high beams to go along with those factory HID's.
for those with sport models, there is a bulb also made by Osram called the 'hyper'. though the name sounds 'ricey', it is indeed NOT. what they did is essentially take an h9 capsule and put it on an h7 base, so you have a bulb that will put out approximately 40% more lumens than a compareable 'high performance' bulb, but only using 10 more watts.
to give an idea of HIR
and Hyper performance, here is a subaru forum link that is a great testimonial-
http://forums.beyond.ca/showthread/t-164266.html