recently i installed forge splitter on my NB. but i set it full DV. i also installed boost gauge. but i noticed that when the boost gauge around 10 in HG, i can hear some hissing sound like the dv valve is opening. and it stop around 5 in HG. is it normal?

I have a 2001 turbo bug 2.0 It has an after market bov. When I'm really trying to move(accelerate) I noticed I get this noise of almost a weak fog horn sound from under my hood. I was going to replace the entire unit, but after reading some threads I was hoping some people can help me...