Originally Posted by Kaz
He also had replaced the valve cover gaskets.
There is the clue. If the gaskets were leaking onto the exhaust manifold, that would have caused smoking and a burned oil smell getting worse until he changed them. My guess is that the caked-on burned oil residue still has enough volatile matter remaining that you smell it when the car warms up. If so, and the leak has been stopped, the smell will eventually diminish and finally go away.