I'm back with the Grand Prix haha

SO this happened twice today. It was downpouring rain and I was on my way to work, there was fog and water vapor everywhere. Randomly as I was driving the check engine light started flashing. It went away as I let off the gas. Then as I was driving home, it did it again but this time for about 2 seconds then went away for the wrest of the ride. I used my big scan tool and cleared the codes, after that nothing happened. When the engine light WAS flashing it came up with a P0306 but nothing actually happened that would call for a cylinder misfire. The car ran totally fine. This was both times. The exhaust has proper flow, the car has: New throttle body and TPS, New crank sensor, New iridium plugs and aftermarket wires, new coil pack on the "misfiring" cylinder new Ignition control module, and I change the oil every 5 to 6k miles. I'm confused because why is it throwing a code but nothings happening while it does? Could it just be because there was so much moisture? The engine bay was wet when I popped the hood.

2007 Pontiac Grand Prix Base

Gm L26 3.8L Series 3

FWD Automatic

163,000 miles