I had a modified airbox for a couple of years (UNI filter, no baffles, cut out bottom and double bell mouths) which worked very well. When I did the BB this winter I went to K&N pods. Because of multiple changes to the set up it, is hard to say for certain, but I do not see any big advantage over the modified airbox. It does seem to be quieter now though, with the bottom out of the airbox it was like a hoover.

05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter