Just as the title states, when I am driving and hit 10 in Hg of vacuum I hear a hiss noise. That is the ONLY spot that it does it. Any other spots in vacuum, nothing. Any parts of boost, nothing. I have ran a thorough boost leak test and everything is fine. I am stumped on what this could be and thought maybe one of you have had the same thing before. Thanks in advance.

 

I got kind of a whine that comes in between -5 to 0 inHg. I haven't figured it out yet...

 

Mines not even in a range, its EXACTLY at 10 vacuum.

9 = no noise
10 = loud "sssssssssssssssssssssssssssssssssssssss"
11= no noise again

I am dumb founded

 

maybe a vacuum leak

 

That was my original thought, but why would it only leak at 10 in Hg

Also , wouldnt it also show up as a boost leak, I thought everything in vacuum would also be in pressure when on boost?

 

i have a open element intake and already get a lot of noise. but i noticed a drop in power and increase in sound around 0-10 hg. i also noticed if im not at full boost, it will drop quickly, as well as not hold as high of a boost at wot.

so the other day i was inspecting my vacuum lines, and right off the boost controller in a vacuum line i found a pinhole leak that had threads coming out of it. after i fixed it, the extra noise stopped, my power increased(back to normal), and put me right back to 24 psi at WOT

 

I'll recheck all my lines again, but I cant beleive it wouldnt have leaked during my boost leak test.