Originally Posted by sporadic
This is not accurately stated. The CFM most certainly is dictated by the turbo, by both the turbine side and the compressor side.
A small turbine housing will restrict flow, and a small compressor will restrict flow.
There is too much over-simplification in your explanation and the original poster needs to do far more reading on their own rather than expect to get all the answers here by non-professionals, including myself.
Go to the Garrett website and read everything before accepting anything you read here as fact.
EDIT: I'll add that I recommend not buying a single piece of your turbo kit until you can read, understand, and plot points on a compressor map relative to your power goals.
If you don't want to do any of this, then just buy a pre-made kit from a company that has done all the research already.
Regardless of what you have for a turbo, your intake track and combustion chamber are not variables. Changing your turbo sizing will not change this. A larger turbo will reduce back pressure, this will result in better evacuation of the combustion chamber...therefor improving the VE of the engine.