I'm sure everyone has their own opinion on all these systems, but I dont think many people have definative answers as to their real weaknesses.
All I'll say is that the likes of Forge and definately, if not more so HKS, do a massive amount of R&D into these products before they go to market, and they certainly dont sell £475 intake systems which dont cut the mustard. HKS especially, were founded by racing engineers, and I've no doubt they'd be mortified to be selling inferior products.
The pipework on my HKS system is extremely thick in comparison to the BSH system and has an extremely different filter to the likes of a K&N design, anyone who's had a HKS 'mushroom' on another car will know what I mean
As I've said there's improvements I personally may make to the system, but I do question whether if they were of any benefit the manufacturer wouldnt have already combatted these issues before it left the factory.
Its a never ending debate but this thread has made me very keen to do the test on various different kits with stock and modded cars, so I'll happily take the lead on it and maybe speak to a magazine and see if they'll support us and feature it? We would just need a few cars and a techy with a laptop to do the logging....sure we can sort that though, and pretty sure the manufactuters would support such a test.