The same design would have similar problems to the OEM system. A better designed header, which terminates in the same position as the OEM header, would be a lot better. You may want to check out Viking Exhaust : When only the best is good enough and email Paul if you have questions or requests.
The problem with the stock header is that it has 3 vertical pipes going into a horizontal. The custom headers have 3 independent pipes which merge in front of the mufflers. I think where they merge is referred to as the collector.