In reaction to Turnerl.
The fluttering is highly unwanted. Although it sounds cool.
Surge can wreck the blades of the compressor. This happens mainly at high rpm's (of the compressor) and low air mass. This is why the bov is designed in the first place. The main function is to increase the air mass that will go through the turbo and keeping it away from the surge line. Besides that the older model turbo's have 270 degree bearings. When the compressor is driven the turbo shaft is pushed one way. When the throttle is closed the turbo is pushed the other way and it depends on the setup of the engine how it gets to the other side. This is off course no problem for the 360 degree bearing turbo's.
Derby