I had a big stutter for a while, and after working with Torrie at Unleashed tuning we found the issue.. A couple of q's. Did you crack the porcelain on the way out or did you have a serious misfire? Second is the orange ring around the base of the porcelain normal?
It was on all of the plugs, and mostly is on yours. Here is a great link I use to see what mine are doing.... Spark Plug Analysis - Technical Information - NGK Spark Plugs Australia