Turbo Waste Gate

[RSM Masser]

Just noticed yesterday that not only do I have a horrible misfire - resulting in a loss of power and uneven running (bizarrely though the exhaust note has improved) I noticed a 'phish' sound when backing off the throttle - like escaping air.
Is this normal or should I be looking at my rough running faults to include turbo air leakage - I have not tried the obvious plugs / coil packs yet.
Car is a 2001 3200 auto

 

[conaero]

That was normal from my memory of my 3200, you build the turbo pressure then the pop off valves dump it when you back off.

 

[CatmanV2]

Stops the turbines from stalling, if you have a wastegate. When the throttle closes, the induction airflow stops, and that can stall the turbine. So keep the air flowing with it's own mass by letting it out of the gate.

C