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Discussion Starter #1
Just started up the stang and took it for a spin. There is a 9psi spring in the waste gate and an 11psi spring in the BOV. The BOV does not open during idle nor after letting off the gas. I have a considerable amount of flutter/surge. Both the WG and the BOV use the same vacuum source. The wastegate opens properly at 9psi.
 

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Wastegates dont work same as BOV.

BOV spring is set to how much vacuum your cam makes,
so that when it sees vac. instead of boost when you close the throttle it blows off.

Your BOV spring doesnt match the vacuum your cam makes.
 

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Discussion Starter #4
Yes I understand that after doing some more research. Would a softer spring let it open up a little bit easier when I'm off the throttle?
 

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It sounds like the BOV has the wrong spring for your combo. What is your idle vacuum? According to tial, here is how the spring pressures correspond to idle vacuum:

12 psi (-22 and -23 in/Hg Vacuum)
11 psi (-18 and -21 in/Hg Vacuum)
9 psi (-14 and -17 in/Hg Vacuum)
7 psi (-10 and -13 in/Hg Vacuum)

The best thing to do would be to get the proper spring. The second best thing would be to cut down your current spring to get it to work. To do it, remove the bov and hook it up to the vacuum source. Start the engine and give the piston a good push. When you push it in and out it should be buttery smooth....with very little resistance (yet remain closed at idle). Start off by cutting 1/4 of a coil at a time until you get the smoothest actuation as possible...but again, while keeping the piston fully closed at idle. This is what I did…and I haven't had any flutter issues since.
 

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I have the same set up, 9psi WG spring and 11psi BOV spring. Change the vacuum source of the BOV to a port on the intake after the TB.
 
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