Fabrication tips

I have the intercooler collecting dust and was wondering what thickness of pipe is the best to use for plumbing it. My welding skills are nothing to brag about, if that has any bearing on what pipe to use. Also what type wire to use in wire feed welder for this application any help is appriciated.

use manderal bent pipe, while most muffler shops dont have a bender in house that can do manderal bends they can order the pieces you want.