I had a lot of the same questions--what would lead the mechanic to question oil pump? I don't know, I was just relating what I've been told. So far, its all hearsay.
I will get some more information when I eyeball it.
The puff of black smoke does sound like unburnt fuel. How solid are the timing chains in these engines--do they jump time?
Thats for the answers, I will provide more information as I get it.