Ahh thanks Red and Falcon! Some things to think about when I get my custom b-pipe made for my G-Limited.
I recently purchased a Fujitsubo Super EX to modify for my BEAMS engine, then a week later I found (after a 5-6 year search) a Phoenix's Power (Garage Fukui SPL) exhaust manifold in Japan.

Falcon
Yep. Spot on as always Red. 
They got exhaust gas recirculation, coupla otha things an a different computer.
And a significantly different exhaust sound.  My 1996 car with the same cat back exhaust as I have on the later car now used to have an annoying whine.  Whereas with the 4 into 1 She actually likes the exhaust note.  Even the splots and splutters on down changes.

Interesting about a different exhaust sound with the different header configurations.
 
When running an aftermarket cat and catback with the stock header system on my gen 2, I had an annoying drone around 100 kph on the freeway. As well as that the exhaust was also just a bit too loud.
Then after I fitted the the Super X set, not only had the drone completely gone but the exhaust was noticeably quieter. So win-win.