I recently replaced my Evo 8 DV with an Evo 9 DV. At first if I would hit 1-2 psi and let off, I would get a bit of flutter, but now that has stopped, and I am hearing the pressure blowing off, with a quick high pitched "ring" sound.

I have an intake, so thats how I can hear the stock BOV

What could this noise be?

 

Sure you didn't put it on backwards. bottom port needs to go to the UICP and the side port to the intake.

After that I'd boost leak test the system

 

^^ its on properly. I put it on the same way the 8 was on. It works fine at high boost, and I have no leaks

 

bump, anybody?

 

videos would help alot. your post is very vague.

 

post a video