Ods are your injectors are causing the issue. With our motors it can be a reoccurring issue with the direct inject and clogging of the injectors due to fuel not being burned off and causing a foul on the plug. I tried a injector cleanse at a fancy euro shop and the problem persisted. Are you plugs pretty rough when you have had to have them swapped? You might try to swap those first and not the coils and see if that can gain you a temporary resolution for the sputtering engine. I always had to swap cylinder 1 and rarely cylinder 2 in order to resolve the issue but it was a temporary fix as the plug would foul in a matter of months again. Cylinder 1 is on the passenger side of the motor as you face it and it shouldn't take very long to swap just cylinder one. I swapped my injectors and haven't run into the issue yet. Hope this info helps you.