Replacing Head gasket -inspecting, cleaning valve stems

That right there is a pattern that was identified in the very earliest months of generation 3, and corroborated by many other reports, long before any of the cars were old enough to think about head gaskets, and the best information that was released a decade ago to explain that specific pattern had to do with a snort of condensed water from the EGR passages.

 

Intermittent rough starts, the kind not caused by head gasket leaks, are most likely the following time the car is started, after it was previously started and run for only short time. Somehow that provokes the water-snorting problem ChapmanF mentioned.