Millenia S 1999 P0431 code

Over the last 14 days once in a while when I stopped the car I could smell something like burnt oil while still in a car. When I opened a hood I do not see any smoke or could find an oil leak visually or by smelling. I have not noticed any excessive use of oil. Today P0431 code sprang out. Is the pre-cat about done or is it something else masquerading as a pre-cat problem? Thanks.

Sometimes the valve cover gaskets will leak around the the spark plug area and let oil in there, giving an oil smell and also causing a misfire which could damage the converters. The precats are built into the maniflods on millenia's. They give a rooten egg smell off if theres too much raw fuel entering them..... was there any other codes?

Thanks for the response. There were no other codes. I cleared the code 4 days ago and it did not come back. There was never a smell of rotten eggs. The smell of burned oil appears irregularly. For the last 4 days no smell at all. I will check leakage of oil around the cover.