Had BBK O/R X befor. I drove around with this "I'm pissed, because my driver side is leaking, and I can't fix it no matter what I do. I paid 120 bucks for this crop, if I know what it'll be, I wouldn't gave 5 bucks for it!!" look on my face.
Now I got Prochamber, as 02mingrayGT said, "riding around with a big ol grin on your face all day"
The prochamber sounds like a combination of both x and h pipes. If look into the prochamber it actually has an X style pattern inside the chamber and the chamber opening acting like a H-pipe. There is some rumble, but at a higher pitch than a true o/r h-pipe.