what exactly does it do? rookie here...haha. i just got my b1 turbo and i was thinking about the intercooler. will a bigger one be better?

 

The turbo is run from exhaust gases therfore the air charge is warm. The cooler the air the denser and therefore the better for combustion. The intercooler which acts as a radiator for the air cools the heated air from the turbo which allows the engine a cooler denser charge of air at the intake which leads to better combustion and more hp. I don't know which model year truck you have but if its 2005 then be careful of the boost as the intercooler has plastic tanks.