I - Intercooler
Intercooler - This is used with a turbocharger, which boosts an engine's power and efficiency by forcing compressed air into the cylinders. When the air is compressed by the turbocharger, the molecules are forced tighter together, which causes friction and heat. An intercooler increases power further by cooling this air.
Using an intercooler means you are getting more oxygen into the fuel/air mix inside the combustion chamber, which creates more efficient combustion. This, in turn, leads to greater economy and power. (See also Cylinders and Turbocharger.)