Have been getting P0301 in 06 Cayman S intermittently for some time. Tried running Techron for a while, didn't seem to do much help. So, mechanic replaced all coils and sparkplugs, car being older anyways. But, engine light came back, same code, P0301. Car is completely stock, about 135k miles, parked in a garage, driven in California with no rain/inclement weather. Car idles a bit rough when cold, seems fine when warmed up. Occasionally catch the CEL blinking on cold idle. Have done lots of searching, lots of people suggest swapping coils/plugs, but all have been changed. Some say could be air oil separator? Other thoughts?