You are 100% correct.
Subaru made these engines to function as a perfect unit.
At stock power levels with no mods.
From looking at dyno charts and making comparisons, when you make 1 modification you run the gamut of related mods to get maximum power out of it.
Looking at the dyno chart Myxalplyx posted of his TMyx intake, even tho his car has cams it followed the stock power curve closely with the better flowing STi filter in the stock airbox.
It made more power than stock with the airbox... but still had the same power characteristics.
With the more free breathing allowed with the ToMyx intake it still followed the same power characteristics... but at the top end seriously pulled away.
This says, to me at least, that the stock airbox is perfect for a stock car... but with a few mods it starts being a bottleneck.
I am interested in maximizing the airflow of the engine.
The engine is designed to have good midrange tq and an acceptable top end.
In my opinion it lays down at least a thousand RPM too early.
I want to see what it does with optimized flow.
Subaru had to follow emissions and low sound requirements, in general this will slow down flow.
I want to dyno the car as stock as I can get it, then after my battery of mods. I fully believe that increasing plenum size will move the powerband up slightly... while sacrificing some midrange for an improved top end pull.
I know the MAF is going to be another power bottleneck.
So I will either be getting an eprom burned or purchasing a chip from LAN.
I know there have been many knowledgeable people do many things with these cars, but there shouldnt be any harm in trying some new things.
My ideas may work... they may be dismal failures.
But I will have fun trying things.
Jim