There is another thread regarding this. I posted a picture of my K&N with the sensor attached. I drilled holes under the K&N logo.
I also posted the picture from
www.se-r.net that shows the $tillen filter where they have the sensor located directly in the center of the chrome cap.
The newer $tillen chrome end cap does not have the K&N logo on it from what I understand.
Go here:
http://www.automotiveforums.com/vbulletin/t4782.html