CEL flashing, on, gone

[PaulDash]

The Boxster is the perfect car for a ski trip, right?

I was out driving today, doing a bit over 170km/h on the highway with lots of snow and sleet on the road and the "I just saved your life" (Traction Control) light blinking every now and then.

Just about when I passed the magical 177777km on the odometer, the CEL light started flashing. As the shoulder was completely covered with snow and with other traffic behind me, I coasted to a nearby exit. On the off-ramp, the CEL stopped flashing but stayed on. I parked, read a few threads from this forum on my phone, and continued on with the CEL light on.

I found a mechanic that was (sort of) open on Sunday. He hooked up a BOSCH diagnostic tool and read codes P0300 P0304 P0305 P0306. He cleared them, ran the engine a few minutes, charged me, then set me on my way. I continued driving for another 200km with no further problems.

Ideas?