Depends how you drive really
For example, with stock turbos i had full boost around the 3000 or so rpm mark.
So the engine would chew through more fuel because i would be making more power at 3000rpm than with my current setup. Therefore, better fuel economy.
However, At the moment, I am at about 85-90% capacity of my 700cc sard injectors at full throttle/boost, over 6000 or so rpm, so fuel economy goes through the roof