Thought it would best to continue this in another thread.

Still wondering about the whoosing sound? Just to clarify, I hear it just as I am letting off the throttle before up-shifting. Could this be coming from the stiffer wastegate spring?

The BPV is another common failure point. Symptoms of failure include the "phs-phs-phs-phs" sound when off throttle. Look for torn diaphragm and check for it sticking (less common). Stock replacement is cheap ($24), or you can get a Bailey, Forge, or TAP valve.

HTH,

Without distroying it?