Which CBE did you purchase? The majority of the aftermarket exhausts for our cars have X pipes from what I can see. ARK, Fast Intentions, Invidia, and top speed to name a few. Generally, X pipes give better results through out the power band as compared to H or Y pipes due to better flow and exhaust scavenging. See below for visual:
H pipe:
https://www.google.com/search?q=y+pi...COb6IyEOG4M%3A
Y pipe:
http://www.jscspeed.com/images/catal...thumb_full.jpg
X pipe:
http://www.garageline.com/277-441-la...pipe-combo.jpg