PMSL @ metering unit being shafted

it's the air rushing back through the turbine blades, thats all the noise is

called it fluttering, cos thats what it's doing (same as a bird, the noise is the air being moved arround)

you can self control the flutter too, dont take foot harshly off accelerator pedal, practise and do it softly or just in the right place and it lasts a little longer