There is a TD6 Vogue in these parts that runs on the Kahn 22" wheels........ Feedback I have had from the local LR Dealer is that the harmonic boom at idle is unbelievable, but can be stopped by not leaving the wagon idling in Drive. Kahn made the owner sign a disclaimer that he would not hold them responsible for any mechanical damage to the RR drive/ transmission - LR will void the warranty if you run on bigger wheels than the standard 18" jobs and have drive train/ transmissions.
I have heard from 3 people with the Kahn RS wheels that the alloy is rather porous and they need to continually ( like 2-3 times a week) re-inflate the tyres. I personnally think the RR looks rediculous on the 22" tyres................. they are OK on a hairdresser's car like the Cayenne but the RR is more of a gentleman's conveyance and doesn't look right with monster wheels. Even worse are the Kahn "sports" exhausts, they look like a row of chromed baked bean cans sticking out of the back, and so far all the Kahn exhausts I have seen look very crudely made....... same goes for the chromed effect Blenheim Vents on the wings - I really fancied a set for my own car until I saw them fitted to an Oslo Blue RR and they are just pop-rivetted on top of the vents and the rivets are easily seen. I DO like the Kahn paint jobs that I have seen though - no black anywhere on the body looks really nice. I do want one of the Range Rover Sport grilles for mine too!
See it here http://www.web-rover.co.uk/?p=articles/rrsport05
and here http://www.keycast.com/keycast/LandRover/RRS/PhotoReveal.asp?marketid=67&langid=2