Maybe a stupid question, but it seems to me that the most efficient design would be the one with the least restrictions, turns, etc and get the exhaust out as quickly as possible (without having no back pressure at all of course).
So why is it that we're seeing so many styles that seem to have a single shared muffler for the two pipes (eg Nismo and HKS) versus 2 individual mufflers a la Mine's and EXAS Evo.
Single Muffler
Two Mufflers
I'm sure eventually dyno's will tell the tale of what works best, I'm just wondering why we would have the different takes on this, or if one method would be clearly superior.
Also, why no options like this yet