1.4 Auto vacuum problem

I think I have a problem on my 1.4 auto K11.
When I'm trying to slow down a little with the brakes, it feels for the first half of the pedal, like nothing happens, then a bit further down, it brakes like crazy.
So let's say there is no way to slow down in a very controlled way.

What I feel also, is that when I park somewhere, and hold the brake-pedal down, and turn off the car, the pedal comes up really quickly together with a woosh sound coming from somewhere behind the throttle body.
Like air being sucked in.

So my guess is, that it's loosing it's vacuum somewhere.

What I hope, expect i that the stationairy-valve, on the back of the throttle body, is not working well and let's air in, on the moment it should not.
Or, what I also hope / expect, is that the pipes, going in the back of the inlet manifold, maybe are leaking / not sealed well.

How big are my chances on this?
How can I check these both options?

Thanks in advance!
 
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