This seems to be a chronic problem on boosted engines - when I owned my BMW twin-turbo 335 the forums were riddled with this issue. The general rule was to try the following in this order - 1) higher quality fuel, 2) new plugs, 3) new coils, 4) new injectors (cheapest to most expensive). See my post on "Shutter during acceleration" thread - similar issues with my buddy's Dodge were resolved just by switching to better gas (which is the same ting BMW dealer suggested when I started seeing them on my 335). It ended up being the spark plugs on my 335 - as they get older and start seeing wear then the gap opens up and makes them temperamental during cold start-up.