An intercooler is used to stop detonation. It nets you no power. A 5-psi system with an intercooler will produce the same power as a 5-psi system without an intercooler. Now, if you wanted to dial up to 10-psi and experienced detonation, you'd install an intercooler. The intercooler would keep the air being forced into the cylinder cool, and therefore decrease the likelyhood of early detonation.
Cooling the air between the turbo and the engine still yields the same amount of air.
From Superchargersonline: "Essentially, run an intercooler when only when running peak boost (i.e. any more boost would cause detonation) for the octane of fuel you use."
This is just simply wrong.
5-psi of boost at 300* is far less air than 5-psi at 100*.
Less air= Less fuel= Less power.
So even at 5-psi, an intercooler will make more power on any given engine.
And regardless of how restrictive the IC is, if your WG is referenced at the intake, and your getting the boost levels your after at the intake, it doesnt matter how restrictive the IC is, what you need to be concerned about is IC efficiency, and how much it can lower your intake temp.