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Reading your suggestion, I can see where your handle comes from...

Coops, I have an external waste gate, sometimes it would also start barking and buzzing, the car would then jerk and choke when that happened, although that was right near the end. Eventually I found out that the gate's valve had come loose from the actuator and it's membrane. Tightening up the little grub screws fixed the problem. Just a thought that the little flap/valve might be worked loose from it's shaft, that's if the other suggestions don't serve up anything...