Ive done this, gaffa taped up, also i got a hacksaw blade (junior) hand held and cut out the flap piece in there, removed the top lid/cover, then drilled as many holes as i could in the base so it draws air from all over, (bit like drilling the air box on MK2s)
probly makes no differance what so ever, but its nice to know am giving it a fighting chance of getting air, jonnyc's idea is my next move i think, with open fog grilles and the filter down in the back of the bumper area.