X pipe H pipe or side by side

The same reason a 2 into 1 Harley runs stronger than 2 seperate


i can see two in to one pulling each other.
but 4 cylinders in each side should already be doing this.
..Larry Sheppard, (Mopars' head performance engineer for 25 years)
says an H pipe just quietens the system.
i'm no authority,just looking at what make sense.