Porsche has more engineers than both those companies combined
X5
The BMC stuff is a compromise, just like the Chinese headers. They make one size to fit all and typically.. it is too small.
You know:
The stock CaymanS box supports 300hp stock. I have personally dyno'd and tuned this box to 420hp in X51 Cayman's.
We have made our own tubes/air boxes.. too much work.. I can buy this from Porsche and with 15min worth of mods to the box, it bolts in.
I have used the other stuff. The best one I have seen on the dyno is no longer available and was nearly 4x times the price of buying a stock CaymanS air box from Porsche (new)
B