bastaad525 the reason why you STILL hear a flutter, with a BOV, is because the spring for the BOV could be too tight...
When its really tight, or your DSM BOV was crushed, the spring will open and close, open and close, and open and close really fast.
If the spring was loose, the valve will stay open untill the vacuum tells it to close.
The Greddy Type S BOV allows you to adjust the spring tension.. and with it really tight, you will hear it flutter, with it loose you will simply hear a Pshhh.
I personally LOVE flutter sounds, reminds me of the old Audi Quattro Group B rally car, and the older Subaru WRX's in the WRC =)