dang , i wanted to guess the answer before you posted it..and i was right! [egt rises due to unburnt fuel in the exhaust..] But i cheated , it's two stroke experience that gives me the insight on combustion.
btw, guys, you can lean out at 75% throttle if you are cruising and set at a borderline lean max a/f and then let off throttle to slow down [for say a long slow curve]. You'll go leaner at the off throttle...i've seen pistons do a 4 corner sieze damage and score the walls unmercifully; but i haven't experience with 4 stroke fuel injected engines until now ...i don't know if tccs can catch up in time to prevent damage or not. All i'm sayin is from a combustion stand point in a internal combustion engine, hell yes you better not be too lean at 75% throttle unless your pro drag racing and rebuilding after every few runs.
We jet up a size in carb situations on the pilot jet, to prevent this situation.
