A couple of interesting calculators for determining turbo compressor size and intercooler piping diameter.
According to the notes, the turbo calculator allows you to select a properly sized compressor...it's an intake simulator analyzing flow to give your HP/torque expected based on data about your motor. As with anything, garbage in...garbage out; accuracy of the data will produce best results. Make sure you read the notes.
Gas flow in a pipe calculator computes gas velocity in a tube based on flow, diameter, and temperature. Useful for analyzing intercooler piping flow....does not take into account pipe length. Again, read the notes: