Would the effect be different if the airbox was taken completely off versus leaking air around its fitting on the throttle body? I don't know--just asking.
Had the same issue recently. There is a group of vac hoses that connect to the MAP sensor under the tank. if they got knocked loose (easier to do than it should be) the bike won't idle and run like $hit (spit, sputter, high idle then no idle and miss something fierce). The bike will throw a fault code which can be read and corrected by TuneECU (what I did). If this is the culprit your check engine light should be on.