I've had two engine "hiccups" in the last year. The first one was a bit scary, during approach over the sea, without any suitable field for safe emergency landing. The second was in the vicinity of two airfields at full power low-level operation (in order to avoid delay), which really scared me, for the next 10 minutes I was only thinking how I f**** the engine. But in both cases, it seems that only a cylinder didn't fire, since no water was found before and after each "hiccup flight", engine has performed without any sign of problem during the rest of both flights and on every other occasion I've flown the aircraft.