There is some sort of vacuum operated butterfly valve in the air intake. Im assuming that this only opens under heavy acceleration. Was thinking about ditching the butterfly. Some sort of custom made funnel that directs air from behind the grill up to the intake would surely increase flow into the airbox. The size of the air intake is quite small so any way of diverting more air into it would surely be a benefit to the huge bore throttle body. The stock toyota filter looks pretty restrictive and there is also another filter in the top of the airbox before the throttle body. I think increasing the air flow to the box on the standard set up is the best way to go.
