Originally Posted by GPSHSLAX
I don't know where you can get pipe mandrel bent, but if not realize your 4" pipe could pinch down easily to the same diameter as 3" when you bend it 90 degrees. The 3" pipe could pinch down even more obviously. Also depending onthe conductive properties of the material used the engine heat will warm the pipe and soak some of the heat into air passing through it. Plastic has less of a tendency to do that. The PVC I used was a thick walled cellular foam core tube. It has good insulative qualities. I don't know what it is used for in real life, but it was perfect for my application.
the question i have is do you think there would be a diffence from this to a lets say aem brute force since those are smooth on the inside verse this becasue its not going to be completly smooth where the couplers are you will have a step up to those.. but then again it must be better then stock