Originally Posted by bulla

Honestly to me the noise your are describing sounds to me like turbo surge. If it is surge it can be very damaging, eventualy leading your turbo to its death! We just need to verify that's what it is to get it resolved. A boost leak isn't normaly heard unless around the up pipes or a boot blown off. Best thing to do is give your boots a once over and verify they are all tight and inspect for soot around the up pipes. Let us know what you find.