You are totally right. My setup should not bring any direct performance benefit. I mainly did it because I like to tinker and I also have a few buddies who are planning to run higher power figures.I'm no expert but I saw something similar in the Yaris GR4 (see below) being developed and it was considered to be of no benefit. Given the air has to do a right angle to head towards the turbo wouldn't this lower it efficiency/clash with the normal intake?
I don't want to be a downer, it looks awesome I just don't want you to go through so much effort in vain.
I believe the stock air setup (to provide air to the airbox) is not perfect with higher power numbers.
Of course I cannot prove this, but I don't think more air in the airbox would create any downsides, since the stock intake and turbo inlet already limit the amount of air that can reach the turbo.
In my opinion the two bottlenecks with the stock air system are a) the turbo inlet and b) this little snorkel-like thingy which is supposed to provide air to the airbox. Both may work with stock power figures but why not tinker a bit to improve things?
I solved b) with my setup and a new turbo inlet will follow soon as well