mine dont do that, its woosh's when dumping boost but flutters when pootling about, i'll try and get a vid up soon as i see others with early APY engines saying the same as me.
I would say thats pretty normal. Its all dependant on throttle position and rpm etc
If your on full throttle and snap the throttle shut the dump valve, or blow off valve (BOV) as we call it in Australia, will fly open and give you the wooshing noise. This is obviously normal
If your driving around on light throttle the BOV will tend to stay shut and give you the chatter, or flutter, you are hearing. If the BOV was adjustable i would say loosen the spring pressure to allow it to open easier, but being a stock car i doubt this is possible.
You hear people saying their turbo broke because of this chatter, then you hear stories of people running around with no BOV, which will make the car chatter like absolute crazy, and their turbo is still going strong.
It seems to be very hit and miss.
Is it bad for your turbo???? if your running high boost and your hearing it i would say yes, if its only on light throttle with small ammounts of boost i would say you wont have to many issues as it really doesnt take much air to make this noise, especially if you have a short inlet.
If your hearing it while accelarating its called compressor surge and i would get the car looked at ASAP. This is normally caused by a bodgy mismatched turbo that someone has built or a problem and it should be fixed.