The thing is, the standard airbox is not particularly restictive, has a cold air feed (under wheel arch) and is plastic so doesn't suffer from heat soak.

There aint a lot you can do with it to make it any better other than the GTA pipe and Hi flow element IMO.

If you are after good performance per pund you might be better off looking at cams, remaps and exhaust. Then start thinking of gas flowing things.

Also remember that plastic topped TS engine have a tuned intake system, which will not work as well if the cone is removed from the airbox.
The cone is there to reflect negative pressure waves back down the intake and this assists in filling the cylinders, the reason it is cone shaped is so that it works over a wider rev band.