The Mr. Gas is just a merge point between and flow does not actually intersect.
Exactly Chris. It's not just a matter of welding two pipes together. Dyno tests etc... have to be done to prove that the design works. And most people wouldn't even be able to tell the difference with seat of the pants comparisons.
X-pipes generally work best on high HP engines where you're rpm's are up there, not much help on your average car.