Mine had these symptoms, yours may not be this but this is what I did to cure it; (Mine is a 1.8T AUM)
.Replaced Plugs & Coils
.Replaced Map Sensor (I also had intermittent boost issues which this solved)
.Replaced both Crank & Cam Sensors (This stopped my "Misfiring" as my crank sensor was wet & not functioning correctly)
.Changed Coolant temp sensor (Cured my non-starting issues as my plug was again drowned in water causing electrical issues)
Hope this helps, if not at least give you an idea where to look