I have added turn signals , brake and running lights to the rear of my Valk , the turn signals work in unison with the OEM turn signals .
They did not at first work correctly , but a simple adjustment to the controller fixed it .
If any one is interested , you can find them here http://www.skenedesign.com/lights/
I am also installing their front lights and turn signal controller , too .
I had the same thing on my BMW and they worked well .