My two cents on the subject of installing the HID's (XENON) in your 928...
1. The Phillips H-4 kit is by far the best available aftermarket out there
(Phillips ballast, Phillips bulbs). I picked up their kit for $520 shipped,
and installed it in my bike (since I only needed one bulb, sold the other
half to someone else with a bike). Getting it to fit is a whole other story
(bike's H-4 mounting system is different than how a car uses it with the
spring in the back holding it in place. Also the lead off the ballast is
only 6-8 inches). I didn't see a problem with beam pattern, had to adjust
the level of the beam slightly, but it did pass state inspection (and the
shop was biased, they were trying to find a reason to fail it because of the
lights...they actually measured the beam pattern's width/length/height),
field of vision is wider and longer (although not much more, mostly just a
little wider but still in DOT specs). I do get flashed by other cars
(thinking I've got my high beams on), but on the bike I'd rather have people
be obnoxiously aware of me, than not. Also, the light is now whiter, less
shadowing on the road and awesome for picking out potholes. Technically the
beam pattern does not go above what standard low beams would, just looks
like I've got 100w high beams directed down in the low beam range. As far
as the beam pattern being low and loosing long vision, doesn't affect me
since I've got three bulbs (1 low, 2 high). My highs are 100w and if I'm
not in traffic, they're on. The low is on for daytime driving (i.e. I want
to draw attention and have people notice me), or traffic at night where I'm
more concerned with my immediate surroundings. Can't say how this would
work on a car in the same situations.
2. I don't see waterproofing a problem. The ballast is sealed, the connectors all have rubber gaskets on them, it still attaches to your headlight the same way your stock plug did (the ballast just basically plugs in-between the stock plug and bulb). I could see your original wiring being a problem, but on my bike it wasn't (already the wiring was so short, and the wiring was brand new and thicker than needed since it also has to handle the higher wattage bulbs the Euro bikes get). 1 year, about 2k miles and no problems at all, even drove in heavy rain (i.e. 40 ft visibility) for 6 hours straight. Did notice the glass is actually cooler than what the stock bulb was. Just have to comment these bulbs in the rain are awesome, so much easier to drive with than stock...although I did get stuck leading the groupall the way home because of it.
3. This is where I see a problem...HIDs (XENON) bulbs vaporize Mercury (now
I may be getting some of the details wrong here, but the general concept is
the problem). When the bulb cools, the Mercury condenses on the inside of
the bulb again. There is a thin wire that the mercury has to condense on
(and a small metal tray under that). The bulb has to be within 15 degrees
of horizontal in order for the Mercury to condense in the proper place. This process takes about 15 minutes. If the bulb is outside of this position, the mercury will condense somewhere else, and when turn on the lights, it won't vaporize right, and the bulb will "blow" (not sure if the guy at Phillips meant actually blowing up, or just not working). The 928's light would have to sit in the upright position for at least 15 minutes before they could be turned off and put down. You could of course turn the
car off, then turn the lights off, leaving the lights up, but the one time you forget (or someone else is driving, or you give it to a valet), you destroy your bulbs (at about $45 each). Mounting the ballast could probably be done easily by putting it in the housing of the headlight (like I said, the lead is only 6-8" long), but they're fragile. One of mine was damaged in shipping and it was packed pretty well. I'd be afraid that the up and down of the light might damage it somehow...although I could be wrong here, maybe it could take it, I've never paid attention to the lights when they go down, is it really smooth or does it hit a "stop" and shake the housing slightly? I guess you could also rig up some type of delay to keep the lights up at least 15 minutes (could probably rewire a "turbo timer" to do this) before going down.
If anyone is interested in ordering, a guy from the supra list (www.mkiv.com, Peter Shieh, email@example.com) put together a group buy with Phillips for $520 shipped (two Philips bulbs, two Philips ballasts, two wiring harnesses, worthless instructions on installation. Made by Phoenix Micro-Lite, with 5 yr warranty, with a serial number so you don't need a receipt to exchange it).
4. ECE (European-code) headlamps. Looked into this with my supra (94TT).
The glass changes the beam pattern to a taller and more direct beam. It also blinded other cars on the road. Seems since they drive on the other side of the road, the right lens is designed to direct light further down the shoulder of the road and is a little higher than the right side (which would be hitting opposing traffic). Driving on the right side of the road, you're screwed, less vision down the shoulder, blinding opposing traffic. Not sure if the same is true for Porsche, but I would imagine so.
5. What I'd like to see is the HID's installed in place of the fog lights
(I know PIAA makes a complete kit, but it includes a round housing). You
could then drive around in town with just these on and have ample light. Go
above 45 mph and put your regular lights up and use stock lows/highs and
still have the HID's complimenting (and improving) the immediate area in
front of the car, and you'd still have stock lights to fill in any gaps that might result from any differences in beam pattern, etc). If anyone wants to help me with this project, I'm willing to buy the kit and hack apart my bumper and fog lights to get it to work. Contact me off the list to discuss further.
6. Another option would be to buy the complete assembly from Porsche (I
believe it's for the 2001 boxster/911), and retrofit the assembly onto the
911...of course if you wanted your shark to look like a 911 knock-off you'd
probably be cheaper to buy a beetle and retrofit a "whale tail" :)