Ive got the same annoying whistle, let me know if you find it. I havent had time to build a pressure test to look for it. Short version is unhook from the turbo outlet and from the intake side. Block one off and make a plug with a valve stem on it so you can pressurize the thing and listen for leaks.any suggestions on how to look for a boost leak
soapy water always comes in handy for finding them as well.