Unless you're making serious numbers, crush bent IC pipes will not inhibit performance in any noticeable way. Whereas exhaust needs to flow through the system as quickly as possible (making mandrel ideal), IC pipes are just pressurized, meaning that the flow of the air through it is so quick already, that crush bent will work fine. The reason we do metal IC pipes is not cause of their shape, but because they do not expand. As long as they are metal you are gaining the full benefit of doing metal IC pipes.