99 Honda Civic Misfiring Issue?

I have a 99 Honda Civic LX with over 200k miles. A few months ago I had new spark plugs and wires installed, and even more recently a new distributor cap. Currently the engine misfires a little on startup before it levels out and runs smoothly. After driving for a few minutes it will start to mildly misfire while idling, and worsens when I accelerate. Other times it is fine until I hit 50-55mph, at which point it strongly misfires. Revving the engine will make the misfiring stop until it downshifts. I tried some fuel injector cleaner with no luck. I'm leaning towards the igniter but would like to hear your opinions.

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