Incorrect Timing Adjustment causing heat issues?

My understanding is the hottest temperatures are generated around the rich side of stoich. (I'll have to dig that info out to verify)
A very lean condition will result in loss of power. That's how it normally shows up when driving. When its happened to me, the engine has revved and then died. Sometimes it will catch again, especially if when the throttle is closed down somewhat.
At idle, a lean condition will show up when load is applied. With automatics, that is as simple as placing it in gear. The little additional load from the transmission pump will cause the rpms to noticably drop.