How do I have compressor surge out of nowhere?

[im2bad4ya]

I'm running a T25 turbo with my wastegate set to boost at 9psi and have a Greddy type S BOV. So I installed my JDM engine this February and I've been running fine with my setup, BOV works perfectly with the classic Type S whistle. Then starting last week my whistle went away and now I have compressor surge. I don't have any vac leaks and I checked both the wastegate and BOV for leaks but they're both fine. I also opened up the BOV to check for rips in the diaphragm and it's good. What else could cause my compressor surge??

 

[dirtysouth_msp]

Check to see if BOV opens with handheld vacuum pump.

 

[tweety2300]

Try loosening the spring on the bov. Just turn it to softer setting on top of it. Cheap eBay bovs need to be readjusted here and there