Hi Chris, the old cast iron split manifolds not only help the engine breath better, they also make the engine not sound like it is working its nuts off while under load. depending on what type of mufflers you decide to use will decide the sound you get. I use a set of the old turbo mufflers and it is very quiet unless I want to wind her up.Then you get the split manifold sound. Using an equalizer tube between the two pipes before the mufflers will also mellow it out some more.
