Standard airbox's are black plastic things which have a panel filter inside.
ARC airbox's which Nismoman is talking about are alloy and bigger capacity and have an arc panel filter inside.
airboxes dont flow anyless then a pod filter really unless you have the air flow blocked off, but then your a nob.
People put boxes around pods to premote cooler air intake, so blocking off the engine back from the air filter...works a treat.
oh and maybe get your injectors cleaned, maybe that will help.
I am still running stock rb25 injectors for 280rwkw.
Edit: But I do have a fuel reg, and big fuel pump.