All I know is a more straight through design usually makes more power AKA Gintani.
I've had many systems, all of which are two muffler systems. They all seem to have a big trouble to look perfectly equal on both sides. The only system I did not have this problem was the Gintani. I still can't understand why that one was perfect, while I'm having trouble with my Dinan and had trouble with my Remus.
2009 E92 M3 | Alpine White | Black Extended | Advan RS | Turner Test Pipes | Dinan Axle-Back | OETuning | Eibach Springs | UUC SSK | VRS Front Lip | VRS Type I Diffuser | Matte Black | RPi Scoops | MS Filter | Yokohama AD08 | F1 Pinnacle
Special Thanks: Gintani | OETuning | eAs