Best to remove and clean the windscreen washer jets from the bonnet and refit them using a bit of sealant as that is a common source of water ingress above the coil packs.
Another possibility for causing a misfire is the main engine harness plug at the back left side of the engine bay on the bulkhead (when standing at the front of the car). It's the connector with a bolt to retain it in place. Remove the bolt, unplug and check for slight corrosion and clean with a good deoxidising electrical spray like Servisol.