[satz]

Originally Posted by //TMT

Do you mean lifting off when still in the carpark? That's probably just manifold vacuum rippling through various nooks and crannies. With the wastegate open for warmup, and no real load to call for boost anyway, it isn't from there.

Lifting off on the road is another matter. There, it's the wastegate opening, which changes the exhaust flow direction, and also the blowoff opening, which causes the boost to recirculate round'n'round until flushed through the engine.

hi TNT, I can accept the wastegate sound (though it's def louder than my old twin turbo 335i), but it's the high pitched 'hiss' when accelerating (before lifting off throttle) that's interesting. I can hear this when driving in the open as well (when my window's open)...

cheers