Mike,
I honestly wouldn't bother.
The NA BMW engines don't have much to offer from a remap. Unless you are able to have someone tune it, whilst the car is at a rolling road, I'd be very cautious when reading bhp gains from remaps.
As a start, why not get your car on a rolling road and see what power it is producing. I'm not sure where you are based but if you are in the South, I can recommend someone who has experience with Aeros.
Getting real gains from an NA BMW V8 isn't simply about a remap, it starts a slippery slope of many different component changes AND almost all are expensive.
If your car hasn't had it done, one modification that isn't expensive and many believe adds power and smoother power delivery is to improve the airflow into the airbox. This is done by drilling it and adding a more efficient air filter (K&N, BMP, etc). The factory did mine, so I cannot tell you what the best process is but I can ask the question if no one has done it themselves and is able to detail the process.
