Courtesy of Club Lexus:

Member there has a 2006 Lexus IS and finds that the electric power steering on the car jerks wildly when the headlamps activate. Problem is traced to the installation of an aftermarket HID ballast.

Here's the original post and follow-up.

Crazy stuff. How probable is it that the ballast is producing enough electromagnetic interference to affect a position sensor within the steering rack? Are Hall effect sensors particularly sensitive to EMI / RFI?