Some dvs make different sounds so the make might point to the sound. HKS ssqv makes a hight pitched squeak, others the whooooosh. These are all vta(vent to atmosphere) dvs. To silence it you could fit a re-circ dv. The chatter sound is most probably the wastegate...do you have an induction Kit fitted as these can amplify the sound of the wastegate.
VTA.......old hot air expelled, new cold air into the system...cold air+more fuel=slight lag but more power.
Re-circ......hot air re-used with cold air drawn into the system...turbo keeps spooling=less lag but hotter air+less fuel=less lag..less power.
I may of course be talking utter bollox...but this is what I picked up with modifying turbo'd cars.
Antilag is the work of the Devil.......or people who like to rebuild turbos

.....drop the antilag....it's all about launch controll
