I can see both sides, and they both make good points.
Lord knows I can think about stuff, "over think" about stuff and go totally extreme at times. Poor ecoli has probably popped a few headache remedies since I started talking to him about turbos (sorry about that ecoli
). I think there are many factors leading to the correct answers for this.
Several things come to mind, first would be what is the purpose of the part in question?
Intercoolers are designed to maximize the air-to-air or air-to-water transfer of heat by ways of increased contact with the metal by way of turbulence which is purposely caused by internal design of the cores . I think it would be very important to take every bit of opportunity to help with that effect.
Intercooler piping is a means to move the air from one place to another.
I'm sure that there is some effect from the different metals used, but in our applications, would we really see a difference? The air flow is so fast that there really is not much time/contact with the intercooler pipes to really make a difference. I would like to see somebody do a controlled test inviroment (Raptor?) to really find out. Most intercooler routing is really short. To see if there is a difference you would have tap and read temps at each end of each pipe under boosting conditions to find out. I would think the biggest benefit would come from just insulating the pipes with a reflective temp wrap.
As Raptor said, if the added weight kills the benefit from the increased efficiency, what's the point?