I was thinking I should clarify what I was feeling.
At start up when cold I got an erratic idle. It would vary between 500-750RPM. Once warm the idle would be steady in speed, but rough in texture (booming vibration, water in water bottle made lots of ripples).
After replacing the spark plugs still get a little idle variance at start-up, but the engine ran so much quieter. WOT accelerations were the same speed but felt about 60% smoother. When idling warm the engine was insanely quiet.
Error codes obv points to VANOS or coil pack problems. BMW's coil packs kinda suck, but I wouldn't replace them as a maintenance item, only if/when they go bad.
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