Re: breaking in new motor
No, it is not a 4 cycle thing. Full throttle is where the engine generates its full rated horsepower (if propped correctly). Generally speaking, the more horsepower you make (out of limited cubic inches), the shorter the engine life--5000 HP Dragster engines have a service life measured in seconds. 5000 HP locomotive diesels a LOT longer
So, it does stand to reason that extended full throttle operation will reduce service life of the engine. How much? I have never seen studies of this and way back in the early 60s, both Mercury and Chrysler ran their engines wide open, non-stop, for days to prove reliability. So, this just may be another urban myth.
ANYWAY-- extended full throttle operations certainly do reduce the service life of your wallet! LOL