I had the same issue with my E63 when I had it. I am sure that some of the problems can be with turbo lag, but ost of the problems stem from the drive by wire set-up. You can do things to help it, like getting a tune will clear most of it up, but you can never get rid of it all. The other thing that will work is a sprint booster. It actually modifys the drive by wire signal to provide a quuicker response. Whe I got the tune,,,the acceleration improvement and off idle acceleration was improved greatly. This is the route that I would go with. Getting my X5 5.0i in a week, so I will get back on here and share my thoughts about the "lag".