Aveo 2008 Drop RPM at Braking

[Sentaku]

Hello Everybody!

I need your help. I have a 2008 Chevrolet Aveo with a weird problem since 2 months, when a brake on a red light, stop or to turn in a corner the revs drops around 200-300, this issue is not always, sometimes it does or it doesn't.
I changed all filters, spark plugs, Spark plug wires, timing belt is ok, ignition coil is ok. I checked IAC valve and it was dirty, so I cleaned it and throttle body too but the problem persist.

I looked for some vacuum leak or something and all is ok, I don't have check engine light on, so I don't know what is going on! It's driving me crazy . This is a video where you can see the problem https://youtu.be/gfXcejMQ-6g

Update: I noticed something, it doesn't when I brake, it is when I shift into neutral...

Cheers!