Hello buddies ..
I've got similar problems with my XT660Z.
riding at low speeds with the engine warm, the motorcycle begins to choke, failing losing acceleration. at some moments at high, 6000..6500 RPM she cuts without at least reaching 7000RPMs.
coincidence or not, soon began when I changed the stock exhaust for a LEOVINCE, and the only change was to close the injection of air into the exhaust to reduce the levels of carbon dioxide.
what do you think?

P.S .: excuse the English, I do not have socializing
best Regards