Tried to find an appropriate forum, there wasnt an intake so gen. disc. it goes:

Nothing has been changed with the intake but as of the last 2 days its started to hum, under 2000rpm while moving or idle. Its louder in cab but is still plenty loud outside the cab. Airbox vibrates badly so Im sure thats the location of the sound but what is causing this? Filter is cleanish, its getting plenty of air....totally clueless here. only two threads on this problem here, so seems to be rare