Very similar problem to mine, took to a local inpdependant vw garage diagnosed it as a misfire and said someone had broken the coil pack but he'd managed to fix it. Not really knowing any better I left happy thinking my problem had been sorted, a week later te light was back on, a mechanic mate of mine just said to stop by his house and he'd check it, went round and it was misfiring on the same cylinder the garage said they'd fixed, just popped to local motor factors got a new ngk coil pack for 31 quid he fitted and reset the car seemed to sort the problem. Until yday it came back on, it flashed at first then stayed on do I guessed it was a misfire, order myself the little diagnostic computer should come today so I can have a look, then prob just change the rest of the coil packs (which I should have prob done when changing the one??)