So from the graphs of the more aggressive maps it would appear that in the lower gears the boost is just not able to keep up with the requested amount due to the rapid Rpm increase of the engine. In the higher gears 4-5-6 for example as per mine in fifth do you get to see what is proabably the true requested boost and, the additional boost that is requested but not used in the lower gears comes into play.
So in summary, if myself and woody floor it at 70mph in sixth S4tan should easily be able to keep up provided he changes down too gears.