I have an 02 A4 1.8T, and one day while driving my car suddenly had a severe loss of power. There had been no symptoms, so i thought maybe some water had got in the fuel line or on the spark plugs. so i drove it about 5 miles to see if that would fix the problem, and it didnt. I checked the code and it said "cylinder 2 and 4 missfire" we changed the coil packs on those cylinders, and the problem was solved. They cost about $50 a peice here in the U.S. the coil pack is about 6 inches long, and conects to the spark plugs. you can just pull it out from the top of the engine.

Keep a spare coil pack in your trunk. Also, they should only cost around $25