You just argued why a bigger pipe would make sense. The whole point is I am saying the AA diameter is smaller. So if a bigger one like the OEM or every other xpipe flows more than why is AA using a smaller one?
Also there is a point where flow "capability" is much different than flow. If a pipe is too large where gas velocity is too slow or there is simply not enough power to produce gases that are that great or have enough velocity, than flow will actually be less with a larger pipe than a smaller one.
The smallest diameter pipe that allows enough total flow is what gives you the most efficient and most performance.
So this is why I assume AA goes with this. Considering the stock sizes and AA use the same pipe for 600 hp applications which I really wonder why they are not using a bigge rpipe, clearly our pipes have a much larger flow capability than is needed for the NA power it makes and thus a bit smaller of a pipe for NA applications to keep velocity up and actual flow even more with the smaller pipe.
So I actually do understand flow