Nowadays, pretty much every turbocharged vehicle comes with an intercooler from the factory. However, the OEM engineers are shackled by cost, size, and weight. Because of this, they will use an intercooler that fits the minimum requirements to operate at the factory boost levels and airflow. Most of these OEM intercoolers are very thin, use plastic end tanks, and in some cases, they are even located in areas of convenience rather than max performance.
There are two main types of intercooler core design, Tube and Fin, and Bar-and-Plate. Tube and Fin is common in the OEM because it is cheaper and easier to manufacture. It also allows for plenty of airflow through the core which aids in cooling with other things that might be located behind the intercooler, such as radiators and AC Condensers. Tube and Fin intercoolers also typically have lower pressure drop across the core which helps with throttle response. Bar-and-Plate Intercoolers are usually preferred by the aftermarket for their higher cooling capabilities. A well designed Bar-and-Plate intercooler can cool better than a Tube and Fin intercooler while suffering minimally, if any, higher pressure drop across the core.
After you’ve settled on a core design, you should look at the structure of the design. The fin density and design is the biggest factor in intercooler cooling capability. Low density fins will not cool as efficiently as a higher density design. However, if you go too dense, you will increase cooling ability at the cost of increased pressure drop.
A good example of this is found between the design of the Treadstone TR8 and the Treadstone TR8L. The TR8 is has a higher density internal fin structure which allows it to cool more efficiently than the TR8L. However, because the TR8L has a less dense fin structure, it features less pressure drop. Therefore, the TR8 is designed for higher boost applications where pressure drop isn’t as big of an issue and heat management is more important. The TR8L is better suited for low boost applications with large turbos that have much higher flow.