Review on High-Performance Denso 6731300 Ignition Coil: Ensuring Reliable Spark Ignition by Matt Bokil

A 2000 Celica GT threw P0300 and P0304. This means random misfires (p0300) and misfires in the 4th cylinder (p0304). I wasn't sure if it could be a spark plug, wiring or injector problem. First thing I did was change the spark plugs and it really helped for about a week, after which the codes came back. This time I marked the coil that I thought might be bad and moved it from cylinder 4 to cylinder 1. I waited a bit, checked the codes and sure enough, a new code (p0301) followed the suspected bad coil to cylinder 1, I replaced the coil with this item and the car runs smooth again, the code went away in about one Day. The coil matched the car's OEM originals. I was tempted to go with the cheaper aftermarket one, but since the other coils lasted 150,000 miles I figured using an OEM might be worth the cost. I didn't talk about all the coils needing to be replaced, so the other 3 OEM coils still work. Will update as more coils fail.