I'm after a induction kit but I would rather modify the air box so it collects and routes air from the naca duct on the bonnet. I have seen a group A airbox for sale but I wouldn't know if to fit it you would have to swap things around in the engine bay.
Have you seen pictures of Blade's airbox in the other thread?
The gr.a carbox fiber airbox fits without problems but you have to buy a separate blitz or other brand filter, you need to fit the battery somewhere else and to have a custom made alloy,carbon or silicon pipe to the turbo(well probably PE can do one now as they probably made one for blade).
This airbox setup will became expensive, around 600£, but will be one of the best!
You also have the carbon fiber monster sport airbox with the relocation kit, or the alloy spec r airbox with the relocation kit that are not a bad solution.
I have the HKS racing suction kit fitted and I made an hose to bring some fresh air and remove the little plastic restrictor of the naca air intake. It's not an airbox but it works well and looks nice, you don't need to remove the battery and the complete kit is around 300£.
I've seen the filtration test of the hks filter but I can't see how it could be that bad considering that the hks uses the same kind of foam as the motocross bikes, and the foam should be the best for dust.
There is also the pipercross foam filter that is not very expensive and is used in gr.a cars, but then you have to buy a separate alloy pipe if you don't want to keep the plastic standard one.
Saw the same as blade's airbox in a japanese Lancer Evo mag for 53,000 Yen, ~300 pounds. Don't know who's the maker of the box as it just said Gr.A airbox. You don't need a specially made pipe form the filter to the turbo for that, most filter kits with aluminium pipes should be o.k., but you'll have to test before of course.
Thought I let everybody know that there are a few more to choose from. HKS makes both the SPF and a Blitz type wire mesh jobbie. The there is the Blitz mesh type, the Trust Airinx, the Trust normal filter(a version similar to the HKS SPF) and the Apexi paper filter type.