Thought I'd give this thread a bump.
Most of you on here have likely heard the Mazda 787B. It's a fabulously horrifying noise. The engine, of course, is a R26B 4 rotor. Now the engine in the 787B uses, for I presume packaging reasons, a header configuration that merges all four exhaust ports into one outlet. However, there exists another configuration. Mazda's IMSA GTO warriors also used the four rotor engine, but the exhaust had a 4-2 merge but didn't merge further, so that the system has two outlets. Without the second merge, the exhaust takes on a much more layered, lower pitched, and rich sound, rather than the typical scream we associate with the 787B. So here it is:
<a href="http://www.youtube.com/watch?v=zZjmRy0OpK4">YouTube Link</a>