That, along with Docc's use of beer bottles to add bell-shapes to the airbox top suggest that the main restriction on the V11 is getting air to filter - not the filter itself. I think that just ditching the rubber snorkels from the airbox top might allow a bit more air in. The search for the correct shape beer bottle provides intrinsic motivation.
On the theme of airbox mods... I just put a whole new airbox and an enormous pod filter on my 7.3L Turbo-Diesel F250. The new airbox draws in fresh air from the stock intake piece (which opens in front the radiator for cool air. But it also has a huge hole in the back of the airbox, so air intake can flow in from the other side.
I'm no intake scientist, but it seems to me that holes in the V11 airbox lid would serve a similar purpose to the one I just put in my truck, allowing air to flow directly onto the filter (and more evenly over the available surface of the filter), instead of having to travel over the filter to the back of the V11 airbox.