Braking problems, binding!?
 

Ive been having a squishy pedal for a little bit now, but it has become increasingly worse. Now, as im slowing to a stop, I sometimes get a stiffer pedal (like normally stiff, how it should be), then you can audibly hear a popping noise and my brake pedal moves further to the floor, thus also causing me to apply more brake pressure to continue my stop. I can also "feel" this noise in my foot, and it almost feels like the grind you get with worn out pads, but it is NOT the pads, and the noise sounds to be coming from under the hood?

I had Toyota bleed the system this week and it has not changed the feel at all.

I cant find a thread specifically talking about the binding/grinding/pop sound I hear and was wondering if any of you have experienced and fixed this issue.

Thanks

Brake Booster Replacement

https://www.toyota-4runner.org/3560752-post10.html

This could be the issue

I though that was a possibility as well, however im hearing it quietly hum when hitting the brake... could it still be faulty?