15k on my carbed 950 Adventure & I must say I don't know what you are talking about. I live at 5500 feet & regularly go to +8K feet & down to 1K feet & beyond adjusting the idle, with the easy to use & reach knurled knob on the left side of the bike, I have no issues whatsoever with the carbs performance.
FWIW, this may be the best all around bike I've ever owned ... period. It now gets the most use of all the scoots in the garage which include an, a couple of Ducs (1 carbed & 1 injected), an SV650 (carbed), MV Agusta F4 1000 (with a very notchy & sensitive fuel injection map) & a recently departed KLR (carbed).
Fuel injection is as only as good as the mapping. My understanding from some of the dual sport forums is the Euro 990's are having some teething issues with FI surging which some owners are finding unacceptable. When the 990's do hit North America they hopefully will have the mapping figured out.