Some of your cylinders are misfiring, but not all at the same time. A real multiple misfire will show a blinking CEL, not a steady light.

So you go about 5K miles/year. I also suspect that your are not a speed demon. So the plugs could be fouling. You could warm up the engine and then ease the rpms up to 5000 in second gear, followed by an immediate lift off the throttle. That will clean the plugs, but could also get you a speeding ticket!!

Check the crankcase breather system for plugs, leaks.

I doubt the ECU swap will show anything nor improve the situation. A descaling of carbon from the piston chambers might work. Seafoam comes to mind for that.

What kind of spark plugs are in there now? Some of those cheap plugs will stop working after 10K miles. The multi prong iridium have been known to loose a prong.
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Keeping it running is better than buying new