The point is that right now your car circulates the same fluid through the engine, through the radiator, through the IC and through the heat exchanger. That means that when you're engine gets hot, that hot fluid id going through your IC. Then the IC is not cooling the air, it is heating it.

So if you separate the two systems - keep the engine coolant in only the engine and the radiator - and keep the coolant that goes in the IC only in the heat exchanger - you will have a cooler IC and cooler air going into your supercharger.

You may want to look at NeedsWings SuperCooler. It's about $450 and gives a heat exchanger that is four times larger than stock. It also includes vavles to separate the engine coolant from the IC coolant.