Thanks for your inquiry and patience waiting on a response here. We had a customer bring an opened CTS w/ OEM HIDs into our shop and I had a good look inside. We ended up going with the RX350 Bi-Xenon projectors, which required him to make some metal brackets to hold them in place of the stock projector. I also think he lost the AFS (turning) function of the stock HIDs when he did that swap.
One thing to keep in mind here is the new projector uses D2S bulbs, so you would need to plan on also purchasing bulb/ballasts as part of this.
The RX350 projectors can be seen on this page:
http://www.theretrofitsource.com/com...350-sti-r.html.
Let us know what you think of these or if you have any other questions.