I'm about to exchange my Halogen OEM S4 (Audi S4 B5 Canadian Model) headlights against the Xenon OEM S4 (Audi S4 B5 US Model) headlights from someone in Boston. (The person wants Halogen).

What exactly needs to be changed? Will is be a direct bolt-on? Do we have even to change the housings? Please advice...

Or why you not keep your housing , and just buy a HID convertion kit, and use your actual balast

IMO xenon ecodes are the way to go vs NA xenon.
Ecodes thow out more light than OEM .
Having said that yes it is a straight swap.You just won't have the auto-leveling that the US cars do, although the housing should come with the auto leveling motors etc.
Hugh

version kit. Does the guy include the ballast the bulbs, thw wiring and housings or just the headlight assembly.

I'm thinking the next thing to do is tint the xenon housing/reflector/bulb a yellow tinge so that they look like regular halogens... just so people don't follow you and wait for you to park your car so they can make a few $$'s.

<center><img src="http://pictureposter.audiworld.com/41218/ecode_vs_us-spec_beam_pattern.jpg"></center><p>the auto-leveling motor doesn't do any good.

Bw here's a pic of the NA xenon VS. Ecode xenon, can you guess which one is which? ;-)