Top mounted intercooler - is a charge air cooler, a heat exchange device that's typically air-to-air or air-to-liquid type. Used for all types of forced induction internal combustion engines such as turbocharged and supercharged applications. A Top Mounted Intercooler (TMIC) is mounted on the top of the engine whose air exchange is usually aided by the presence of a hood scoop.
The theory behind an intercooler is it allows for improved volumetric efficiency by increasing intake charged air density through cooling (isobaric, constant pressure) by removing the heat of compression that occurs in any gas when its pressure or density is increased. Cooler charge air = more power generated!