I have a '07 and noticed when I accelerate, my HID flicker quickly. It also appears to do it when the traction control is on. Wondering if others have seen this as well and whether or not to be concerned.
Sounds like you have the problem when there is a change in the output/draw from the alternator. Makes me wonder if you may be having a voltage regulator problem. It is an internal piece in the alternator. Just a thought.
I have also never noticed this on my 2009. Is it both lights pulsing or just one? Maybe a ballast for the HID is going bad. Also what is your volt meter doing when the lights pulse? If it is going with the lights you altenator might be going. I have seen a battery that is on the way out make things pulse also. I would have this checked out before something lets go and you are left waiting for a tow truck.