NHTSA Complaint #11608589 — 2015 MAZDA CX-9

We have a 2015 Mazda CX-9 Touring with All-Wheel Drive (AWD). The issue that has been happening is a flashing check engine light (CEL) indicator showing up in the gauge cluster. This issue originally started in October of 2023. I was on the highway doing at least 55 miles per hour (mph). Before the light actually came on, I had already felt the vehicle shaking, and also noticed the acceleration was sluggish. In the blink of an eye, the CEL came on and started flashing. After that point, the CEL stayed on. I was able to get to my destination safely. We took the vehicle to a shop, and told the mechanics the issue, but they could not re-create what happened. We stopped driving the vehicle as much after this first encounter. A couple of months later, the issue still persisted, and we took it to another shop. They changed the spark plugs, and the vehicle had been driving CEL-free for several months. Recently, we were going to take the vehicle out for a drive, and noticed the vehicle shaking (before the CEL officially came on) again. The CEL flashed and came on. As of this moment, the CEL pops up and stays on when starting the vehicle. I put in a code reader, and the code that came up was “PO304 Cylinder 4 Misfire Detected.” We are figuring out what our next plan(s) is/are with the vehicle. I looked at some forums for the 2007-2015 Mazda CX-9 Generation, and I noticed that someone mentioned that there was an issue with the injector pigtail wire (one of the fuel injectors). They also mentioned spark plugs and coil plugs. But they still had an issue and it seemed to be not resolved. I'm wondering if this issue could have a direct or indirect connection with the Takata Airbag recall that was issued on August 13th, 2024 with a "Do Not Drive" alert.