01 stutter

My fiance has an '01 tt non quatro. Today she said out of nowhere the engine started sputtering after she started it. I know very little about Audi's. To me, it seems like it is having a misfire. The engine does sputter under idle and under throttle. Could it be a bad coil pack or spark plug. If a coil pack, how can I check to see which one? Also, I doubt it could be the problem but last summer or fall I changed spark plugs from the ngk to autolites. I know in my ford's, they do not go well, not sure about audi's. Any help would be great. Thanks