Your friend's GTI is German based which means it likely has the ECE based beam (modified to meet DOT requirements), normally referred to as a harmonized DOT beam. These tend to have a sharper light/dark cutoff line meaning less light bleeding above the cutoff to begin with. That GTI may not have much glare when upgraded to xenon.
But Contours for sure produce a lot of glare when you upgrade their halogen fixtures to xenon bulbs, since their beam pattern starts out as more like a fuzz beam from the factory, with not much of a definite cutoff line in the beam. I wish I could have taken a picture of my old 9006 fixture's beam pattern when converted to xenon. The beam against a wall was a mess, and sure they were bright, but everybody would constantly flash at me. And so then I had tried to aim them way down, but then all the light was shining down on the ground in front of the car just to keep people from flashing at me, but now I couldn't see worth a crap for distance vision.
European style ECE beam pattern is definitely a better candidate for attempting halogen to xenon retrofits, than the USA's DOT style beam, although there are some exceptions to that rule, as with your projectors in your Couger (since you said they seem to be OK). Generally it has been my experience (I have professionally done several xenon retrofits for a handful of people in my spare time), but its been my experience that with DOT fixtures results can vary greatly, but most the time the results are not desireable. DOT reflectors, are almost always horrible, although some H4 DOT applications may turn out non glaring, the beam pattern may still not wind up uniform by any means. Many DOT projectors can successfully take a xenon bulb and not cause more glare, but there ARE even a few projector halogen cars that have been known to have problems, as in certain year Acura Integra projectors. The earlier ones tend to cause a lot of glare, and also the Toyota Celica projectors need to have 2 holes filled in on the projector's shield so they wont cause the 'UFO' glare holes. And again, Contours always cause glare. But full-bred ECE fixtures tend to do much better to retrofit. I put ECE 6054s on my truck converted to xenon, with a custom made H4 underbelly shield and they don't cause any glare and those fixtures (reflector) have a very distinct cutoff line with very little light bleeding above. So just food for thought, you can't just stick a bulb with 3x more light intensity in and expect good results, since DOT actually has a requirement for amount of light to bleed above cutoff to light up overhead roadsigns, so when you increase the source by 3x, the required light bleeding above cutoff is also 3x more.
Another important consideration is that, the color blue at bright intensities is the color that is the most sensitive to the retina in the eye, but the color more in the yellow/green range is closer to the center of the visible sprectrum. For this reason, blue seem very bright when they are shining right into your eyes, but the yellowish/white are actually brighter to drive behind. And with 8000k, you'll also find more people over 60 flashing at you, since their retinas don't heal as quick, and blue is most sensitive to that
