I'm familiar with that thread - But it is a comparison of a modified MSDS y-pipe and stock y-pipe.
No figures for an optimized y-pipe.
No figures for the "new design" MSDS y-pipe.
The stock y-pipe is very restrictive, one can only speculate on what an optimized stock y-pipe would do.
The modified MSDS y-pipe was modified optimally. Who know what the redesigned MSDS does.
You cannot say one is better than the other without without actual testing. I'd be interested to see that info.