I wouldnt go 20 an thats too big man. Intercoolers have 1" inch lines, that equals 16an . I wouldnt go bigger then 16an.
Yeah im welding -20 an bungs on my intercooler....we run -20an on my firends mustang and they work well...plus I drive my car on the street alot, so it will help with street driving .....not saying the -16 wouldnt work