Welcome to R-F!
Do you have a check engine light on? If so, take it to your local Autozone or Advance Auto Parts, they'll scan for free and tell you what's wrong.
Also, is it possible to record this humming sound and upload it on here? when a vehicle makes a humming sound, that's a broad statement but you've already narrowed it down to the engine so that's a start.
I'm with nbro, if the MAF was bad it would throw a code triggering the check engine light. -Mike-