2016~2023 CX-9 Brake pedal hissing noise

[nakamx9]

Hello everyone, new Mazda owner here with some questions.
Just got a 2018 CX-9 Touring with 44000 miles on it and break pedal makes hissing or swishing noise in drivers side footwell when depressed. It is coming from brake booster. Also brake pads sometimes click going from reverse to forward. Is my brake booster failing or is this a normal thing for these cars or is it something else?
Video:

https://1drv.ms/a/s!Ar07Dbt_WRFdiJNQqH7x-ubt-nt_MA?e=RJa7Im

Are there any recalls for these? My car is out of warranty. How hard is to replace a brake booster on these, I've done some difficult repairs on cars in past.
Thank ahead for help

 

[PTguy]

This is from the Mazda parts site:

They want $510...you can find a better price. Rock Auto doesn't have the Cardone reman booster in stock.

About the clicking...do you think the pads have been replaced before you got it? Maybe they didn't bother to put in the pad hardware? Rock Auto has the Carlson front hardware kit for $9 and the rear hardware kit for $12. Mazda thinks their kits are worth $41 & $33.

 

[nakamx9]

Thanks for the reply. Looks like rear brake pads and rotors were replaced. Looking at it, they don't seem to have those thin backing plates (correct term?) on them. Will take a closer look when it stops raining to see if hardware kit was replaced, my guess is: NOT.
I did find OEM booster from a dealer for $350.
Was looking at the brake hard piping going across the engine bay and I know I'm going to get yelled for this, but I think there might be a way to replace booster without disconnecting hard piping from the master cylinder. I think if I remove screws that hold AC lines on a firewall there might be just enough give in brake piping to move MC out of the way for booster to slide out. I am short on time, tools and work space to do it right and rather not get into brake bleeding (just sold whole bunch of my tools including 2!!! Motive brake bleeders ((. Going through a divorce)
Any thought?