I just picked up my 2012 GT with 100k miles so I'm going through and replacing basic maintenance parts per the discussion I had with my friend who sold me the car. He told me about the misfire and I initially replaced the plugs just for the sake of maintenance and it seemed to do the trick. About 1000miles later, the misfire came back hard! #3 & #4 cylinders so now I have just replaced the coils, all 8, MSD SF coils. On the initial start-up it did throw a "random misfire on start-up" code. I wonder if that's normal following new coils. I drove it around for awhile, did some pulls and held the RPM at 3-4k where it would really misfire before and basically go into limp mode. So far so good. Can't tell if it's actually fixed yet tho.