Dantruck,
Full throttle is full throttle my friend, butterfly as open as it can be. Perhaps you mean at or close to max POWER that you can use according to the limit chart, that the butterfly is not wide open?
It is by adhering to the limit chart that the pilot "derates" the engine at lower altitudes, but as you climb you will eventually be running at full throttle and quite within the stated limits.
I still think carby icing is also possible at full throttle due to fuel and/or impact icing and not throttle icing. Can any of you icing guru's prove me right or wrong?
Alpinehelicopter,
There is also the possibility you had a stuck valve momentarily, although the engine will run very noticeably rough as it drops a cylinder. It may have only done it for a couple of strokes though. How "sudden" was your power loss?