Technically, it's afterfire, and my 2017 regularly registered a misfire fault via the FordPass app and had a lot of afterfire, although the afterfire only happened immediately after a fuel fill-up. I've only ever used 93 octane. The misfire started happening occasionally after 15,000 miles, and the afterfire started after I added a Roush CAI and Stainless Works exhaust and downpipes. A few weeks ago, I replaced the plugs gapped to .028 and added the JDM tune, and both issues have completely stopped. Unfortunately, I'm now worried about tires and the transmission, because the tune made such a difference, I'm constantly driving in Baja mode/2WD and stomping on it.