Sometimes she has a slightly high idle, which is fine, other times she idles lower like most diesels do. Sometimes she'll idle high for a long time, and sometimes she'll go high....and a minute or two later low...whats the problem?

Lube your throttle linkage.

And problem persists. After a minute or two it idles itself down. The kicker is, if I turn my wheel all the way to the left, or all the way to the right, it idles itself down to normal idle...??

This seems odd, but not a symptom of the engine if turning my wheel fixes the problem?

I am thinking...rack dampener pin? This only happens after its been running for a long time.

Turning your steering wheel puts a pretty good load on your engine.. the power steering pump.. It will lower your idle in just about any car for a second or two.

It stays at low idle for the rest of the time, or may go up high again after like 10 seconds.

My question is, why does this idle high and then go down low after a highway run? Is this built in to the car, is it supposed to do this?

Do you have an idle adjust screw on your dash? I might start looking into that.