I am going to run a 3" 31×12×3 intercooler from vs racing but Is it better to run 2.5 IC piping all the way to the IC and step up to 3" and back down coming out of the IC to 2.5 all the way to the throttle body and step it back to 3" to mount up to the throttle body? Or just run 3" the whole way?

 

On my 31x12x3 intercooler i went 3" everywhere. Didnt give me any problems. Now I am 31x12x4" and still running the 3" charge pipes.

 

Just run 3" the whole way. Basically no benefit to smaller piping except ease of fitment. You could argue it would spool faster but thats a hard sell.

 

How much boost are you running? My setup is going to be about 6-8 psi and the 3" pipe lines up alot better to the TB then the 2.5" anyways but i have also thought of going with a smaller intercooler and maybe just do 3" the whole way or will I not see any benifit with that little of pressure anyways?