Yes i have tried making my own pipes it not the length i am talking about
because the different heat they run at can be countered by changing the length of the pipe to get the sonic wave timing right

Its the reflective properties of carbon versus stainless that kills the power
alloy is better than carbon but not as good as stainless

The down side is the ping ping nosie that stainless tends to make over carbon
but thats the reflection you are after thats making the noise

Carbon will work i agree
But in my experience with pipes it does not make as hp as stainless( but of course its lighter)