Ok can someone please explain to me how the intercooler piping works? Like size differents. Like running 2.5in piping vs. 3.0in piping.
I fig if your running 3in piping your pulling in more air and let out more air.

 

Depends what you want to do ... only difference will be air speed, the slower the air speed the more it has time to cool down, the faster the air speed the less lag you will have ... your intercooler already slows the air enough so IMO just run your piping ID the same size as your turbo's.