Injectors sizes for my mods?

I am about to get a tune and i see where you want to do this when changing injector sizes. What are the advantages to bigger injectors and how do i know what would work best for my mods? I see a catch 22. If i use a computer to get the data for the tune do i want to run the new injectors when i do the test of wait but let them know that i will be changing them?

Since you already have an FMU and inline booster pump, do you have any indication that the system is not providing enough fuel? If all you are running is the blower on a stock heads and cam setup, your stock injectors should be fine with the FMU supplying the extra fuel for the boost.