I have the exact issue you do! and funny enough, I noticed it at the same time! On the way home after buying it!
I asked this same question. Read this thread completely. It should shed some light on it.
http://www.xoutpost.com/bmw-sav-foru...ause-pics.html
EDIT: what you called a "surge" I called a "mis-fire". Just a FYI.