the lower boost button will improve economy! thats why its there if theres less air being put into engine the ecu will put less fuel in.
the factory boost restriction in first and second gear was there for traction!
dan
i disagree with that.
the low boost is much less responsive than on high boost. the turbo actually takes longer to spool on low boost than it does on high boost.
so if the turbo is spooling later in the rev range, you will put your foot down to compensate for the lack in power.
leave it on high boost the turbo spools quicker, and therefore you dont need to put your foot down to compensate.
e.g the vans i have at work, there are some 1.9d and some 1.9td's
we actually get around 5-6 more mpg out of the td's than we do the normal deisels, as the n/a deisels have to be worked much harder to make them move.