When I installed my Greddy Profec e-01, I misinterpreted the second of two ways to perform the installation, which ended up forcing me to run closed wastegate for an entire day. I did run it a bit and I stopped putting my foot in-to it because I would hear a really interesting noise which sounds like a repeated stereotypical duck quack if it displaced 2.0L of air and ran 24 pounds of boost. I have this lingering feeling its either waste gate or boost controller related. What does a bc solenoid actually do? Does a waste gate solenoid constantly adjust the waste gate or would it be either on or off? Reason being I've heard people talk about the bc solenoid clicking and even showing up as knock. I wonder if it is the greddy 3 port boost control solenoid and is only audible over the engine at full boost and therefore varies on load. This fluttering, or quacking, clicking-whatever only occurs when I set the boost over 16 PSI or over 20 PSI when on the manual setting (the Profec e-01 has automatic waste gate duty sensing). I've realized it does it on and off because sometimes you hear it and sometimes you don't. But if you do, you know its there. it's concerning because of its destructive sound. I wouldn't really call this a click tho..But I know someone would.

 

It's the solenoid. If you read through the manual, I think it says somewhere that the noise is normal. I've had the e-01 also and I could hear it sometimes and other times not. I would get into it over and over again to see if that's what it was. I guess it's the valve bleeding off air or something. I'd describe it as a clicking for sure. Really quick intervals.