Sorry to drag this back. But I'm having a similar issue with my '07. It's not turbo lag, it's just as if there's a delay between stepping on the throttle and movement. Like 1/2 second or so. Nothing to do with turbo spool or anything. Literally for that half second, nothing happens then the car gets going. Not a huge deal, but it's annoying when trying to get into traffic. I have a JB4 and that doesn't really help in my case.
Sometimes I end up giving it too much throttle and it takes off. Makes it hard to drive the car smoothly. Is there an issue w/ the electronics? My other car is an Infiniti FX and that car has 0 delay. Even though it's a much slower car overall, it could probably take the 335 up to about 20mph. However, on the newer versions of that car, there was an issue w/ the throttle delay and they recalled them and reprogrammed things, fixed it right away. Didn't know if there was something similar for the BMW.