Three things come to mind:
1) throttle body. It won't cause the low power/miss going up the hill, but when carboned up, will cause funky idle. Some standard carb cleaner and a rag will clean that. Soak the rag with the cleaner and use a screwdriver to hold the throttle open and clean away.
2) One source for the miss could be a bad coil/spark plug. Water can collect down inside the spark plug hole and damage the plug and/or ignition coil. Usually, you can remove them and spot any water issues (will appear rusty or corroded).
3) The last thing, is the possibility of a plugged catalytic converter. That will cause a miss or loss of power, especially climbing up hills. If it is indeed a converter, its covered for 8 years, 80,000 miles under factory emissions warranty.
Hope this helps.