In general day to day use, you will be off boost much more in a bigger turbo powered car. Thats just generally the way it is, the boost threshold is totally different.
My T34 car was making 36psi at little over 2.5k, With a T4 it will be more like 3.5-4k at a minimum, they work well living around 5k.

Its really common for people to see some cruise mpg gains going up in power,if they step to a larger turbo.