Loren (or anyone else),
Are you aware of any control unit differences that would prevent me from undertaking the Bi-Xenon upgrade science project? I checked with my dealer, and it looks like you can buy the requisite parts to do the upgrade. What you would likely NOT get out of the upgrade would be the headlight washers and the auto-leveling/light bending features. Neither of these is crucial to me as 1) I keep my light covers clean (avoids the glare problem) and 2) I do not carry heavy loads that change the vehicle's geometry.
From the diagrams I saw (without part numbers!

), the housing assembly comes with all the basic parts. Thus the order would include the base housing, the ballast, the bulb itself, and the wiring harness pigtail. Do the Cayenne manuals describe any other differences between the halogen and Bi-Xenon setups? Just curious.
Since I bought my "S" off of the dealer's floor, and it was an aearly run, the dealer had not ordered the car with Bi-Xenons!

I'm getting tired of driving with halogens and want to upgrade to Bi-Xenons. I know that Porsche has not released a Tequipment upgrade, nor has anyone else, but this should not be a big deal. I did this upgrade on my 03 ML350 and it worked like a charm. The upgrade required some investigation on the wiring harness and movement of some pins in the pigtail to line up properly. Once done, I got my MB service tech to change the control unit setting from halogen to Bi-Xenon and it all worked fine! (Apparently, MB manages the voltage and amperage to the headlights, so a setting of halogen prevented the ballast from getting enough juice to fire the lights up. It caused the lights to strobe madly.)
Anyway, would apprecaite your thoughts on this before I go drop north of $2K on a science project!

Thanks.
Toby