Yeah mate if the intercooler is to big I'm told you can have pressure drop any way,and the manufacturer should be able to tell you it's flow rate.
I have a calc somewhere to help work out an engines N-A air flow volume rate, but recon if a turbo is thrown into the mix you would need to take boost into affect, my point is, there is probably a calculation for working this out, I just don't have it to pass on. someone out there may?.
Cheers