Seems to me that there is some valves opening and closing when driving.

lets say I do a pull up to fifth gear and release the gas,
i clearly hear a weird sound like a valve opening and brings the exhaust sound higher and if I give it more gas or just try to boost it, the sound is intense and past 4500rpm the boost won't exceed over 0,5bar at the gauge.

i had the same problem some time ago with the stock ECU, not sure how I solved it but I checked every hose and vacuum line and fixated them properly.

and after the pfc install it's here again.

any hints to what it could be?

 

did you replace your check valves?

sounds like you are hearing the sound of the turbo control valve opening and closing.