Originally Posted by Optimiser

That's exactly the same noise I get from the Tial BOV tht came with my A to A kit. The difference is that yours seems to happen much more often than mine, even when you change gears. Mine ONLY happens when I'm cruising along at a steady 100KMH (60MPH in "Retardistan" and I'm at 0 on my boost gauge. With those conditions in continually makes the same noise as yours.