what size intercooler pipe work

[bobert]

I am currently in the process of putting my rex back together. I have just put in my street ported engine and a garrett to4r turbo.
now I am at the stage of making my intercooler pipe work. I am using my own custom front mount ic. I am going to use 3 inch pipe work from the exit of the ic to the greddy elbow but I am unshore what size to use out of the turbo to the intercooler.
what size pipe work do you people use?