P.S. After doing over 60000 miles in my 135i and now over 45000 miles in the 1M. I have concluded (at least in my own cars and style of driving) that Map 8 does NOT help with fuel savings. I've done many 320 mile (tank full) trips with it entirely on Map 8 and did not notice any difference than with the turbo maps.
Why would car manufacturers add turbos for fuel economy? Because the turbos save fuel. It's just up to the driver to not have a lead foot.
(I'm guilty as well!)