A p0300 only indicated the PCM has detected a misfire but not which specific cylinder/s. If you can get a misfire count for all cylinders you could locate which one/s have the highest count and go from there. Being a v6 I would suspect a coil given your description, but don't change any parts until you can be certain you are changing the correct part. Often on the 3.6 you'll get a misfire from a coil under certain conditions which can be hard to duplicate.
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