OK you have 3 purchasable (as opposed to MAKING IT) options.
1) K&N replacement filter under the seat.
2) K&N under the tank attached to the rear of the inner plenum.
3) Triple K&N's direct to the Throttle Bodies.
1) I doubt there's any gain except you get to clean it rather than replace it when it's dirty.
2) Frees up the filter box for "gubbins". Very marginal improvement in potential air flow as you bypass the "snorkels" built into the seat.
3) Allows more air to flow at higher rpms. And allows you easier access to the throttle body adjustment screws.
1) Personally I cant see the benefit of this.
3) I've read actually flows worse at low rpms - and to get the benefit you really will need headers that let the beast breathe out better. And they can be as noisy as hell - mine (2009) is very loud at 2250-2750rpms with triples irrespective of load and secondary butterfly positions. VERY horrid slapping sound. And it whistles a bit too at times.
2) I ran with this until recently making my own modified plenum (similar to Battersea's but a little more "open"). No perceptible increase in noise over stock, breathes well enough with different headers such that one would be detained and locked away if caught. The monster will hit well over 200kph (5000rpm in 5th) with no effort at all fully dressed (screen and luggage) and 2 up. I used a Pipercross PK003F but others have used a K&N.
I would not fit triples again. I'd rather refit the plenum. Option 2 worked well for me.
K&N filter available from Flip.
http://www.flipmeisters.com/product...tank-air-filter-all-models-except-r3-touring/