Originally Posted by 370Ztune

Some companies have proven that a single, larger diameter piping that splits into two smaller diameter piping can provide better benefit. This design can change anything, performance, sound, weight, etc. It all depends on what the company's goals are for the exhaust.

For example, Amuse has two versions of their exhaust, the RS-Silent and the R1 Extra. The RS-Silent is two separate pipes and has a lower, more beefy tone. The R1 Extra is lighter, louder, and has a little bit more performance.

Here are some pictures and links for additional reference:

RS-Silent


R1 Extra