I get break squeal every so often, also under very light breaking. Back off the break, reapply, and it goes away. I also get the break pedal vibration, very minute, and ONLY when the engine is warming up. I've not noticed it once the temp readout under the turbo guage starts registering a temperature. Not that I'm implying the two are related.
I have to agree, that the engine sounds different when not in gear and revving. From what I can tell, the waste gate is held open preventing any pressure buildup.
All in all, I still love the hell outta this car!