My stock evo 9 BOV has started fluttering real bad at about half throttle but full throttle it holds boost like a champ. I tried cleaning it but that hasn't made a difference.

Is there a BOV that I should replace the stock one with or should I buy another stock one?

 

could have taken a dump on you depending on much boost and mileage its seen

 

That's what I'm thinking 29PSI car has 42k miles on it.

 

i had a forge had the exact same issues. Switched to a tial and its great now.

 

Same thing is happening with my Greddy type R. Holds boost well but doesn't open at low boost at all...

 

You have the spring too tight my friend