If this happens when pressing or holding the brakes then yes, it most likely is the booster. The fact that this was a used booster, I imagine it has a leak in the diaphragm and when you are putting pressure on it, it releases and you hear the noise of it passing the diaphragm.
I doubt there is a warranty on that part so you would have to pay for another one. So if the brakes are operating and the pedal does not drop when this happens, I would try to ignore it.
However, if you feel something in the pedal and this "kick" is at the same time, then I would take it back and show the mechanic and see if they place where he got the part has any sort of return policy.
Let me know what questions you have. Thanks
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Tuesday, November 24th, 2020 AT 4:47 PM