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I suspect that you have a ignition coil starting to fail. Eventually the check engine light will come on to help you know what ignition coil is causing your concern. You can also bring it to a Mazda dealer and they can hook up to your computer and run a test to determine which cylinder is misfiring while running. You can also replace all 6 ignition coils.
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Your engine should have 6 ignition coil. At higher RPM when less load and stress is placed on the ignition coil, the misfire may not be noticed. During acceleration is when the engine misfire is most noticeable.
I suggest replacing the 3 under the intake manifold and test drive for change. The front coils are easy to change and swap if necessary between test drives.
Make sure there is no sign of water or oil in the spark plug coil hole. The oil or water will cause the ignition coil to arc to ground and not at the spark plug.