The smell started as a slight smell only occasionally when stopped after driving once warmed up. It seemed to coincide with my changing from conventional oil to full synthetic. I was the third owner and the previous owners changed oil at the proper intervals. I bought the car with 155000 miles and owned it for a year and 10000 miles before the smell started.

Quick solution here... details later.

Replacing the valve cover gaskets almost immediately stopped the smell, (after 30 minutes of driving to burn off the original residue.)

Thankfully this is a much cheaper fix than the front engine cover. $360 vs $1250 and it's simple enough that if you can change your own spark plugs on this engine, you can change these gaskets.

At this point I'm not sure if there is any leakage from the front engine cover or if what I see is just residue from the valve cover gasket. I'll keep monitoring and will update if there are any changes.

Longer story here:

I noticed oil residue under the engine and on the exhaust system just below the engine and it looked like the oil was coming from the front engine cover and crank seal dripping on the exhaust pipes.

I was told the front engine cover was a known culprit on these engines and was quoted over $1100 for replacing the front engine gaskets so I chose to fabricate a deflector to deflect the dripping oil from the exhaust pipe.

This resulted in almost no more visible residue on the exhaust pipe but no change in the smell, in fact it got worse over the next year.

I looked closer, which is difficult to do on this engine because of it's size and fit in the compartment, and I saw oil residue right below the rear valve cover gasket, but the front valve cover gasket looked OK.

I replaced the valve cover gaskets and found that the rear gasket was very brittle and had a crack in it. Probably due to the proximity to the exhaust manifold and no cooling air flow in that area.

It turns out that the rear valve cover gasket was leaking oil onto the rear exhaust manifold in an area not visible unless you remove the upper intake manifold runners like you would when changing spark plugs.