I actually disagree with the above assesment of when an auxiliary heat exchanger is necessary. On the street, you are not likely to do more than a 1-4 pull. If the system has enough capacity, the liquid won't be heat soaked in the less than 60 seconds that takes in a boosted system. On a track (not a drag strip), you are out for at least 10 minutes, hammering the go pedal. You certainly need much more capacity and a heat exchanger installed in a manner to get enough air through it to shed as much heat as possible.
That being said, I think it is rather daft to not have a liquid to air intercooler system without a decent sized heat exchanger. There is very little penalty for having more capacity than necessary, except for a few extra pounds (which is more than made up for with forced induction, and on a FWD car, the additional weight in front of the driveline is actually good for traction and if kept low, won't effect the center of gravity too detrimentally).
If one datalogged a few temperatures and had an accurate dyno plot, you could actually calculate out exactly how much capacity the system would need to within a few ounces. The math isn't too complicated, but it is involved as you would have to figure out the mass flow through the engine, the efficiency of the turbo, the efficiency of the primary heat exchanger, usually found through datalogging pre- and post- temps, and a few other bits of info that are easily obtained.
Modern air/air intercooler cores are much better than they used to be, but, they will NEVER match the overall system efficiency possible with a heat exchange media with a much higher heat capacity than air, such as water, though a coolant/water mixture is much better at exchanging heat more quickly than straight water, and is better for what you are building the system out of than even distilled water. There are several ways to approach this, too. A typical coolant mix is very common, but if the secondary heat exchanger is large enough and made to function well enough in use, you could use a variety of other liquids that have much faster heat transfer rates if you have enough flow capacity in the system to move the liquid fast enough to keep up with the actual heat exchange happening.
Yeah . . . I've thought about this a little. heh