If you believe the coil is good then I would also go back to stock copper plugs and gapped to the spec on the sticker on your car. I had put double platnium in my 07 and on a trip from Atlanta to NY I fouled out two spark plug at the South Carolina and North Carolina boarder at 2a.m....... The dealer that installed the correct plugs said that platnium plugs do not fire as hot as the copper plugs do which caused the misfire. I would do a Seafoam treatment. If you do not know how to do it just go to you tube and watch some of the videos.