2004 3.9 oil drip on driver's side exhaust downpipe
 

Hi, all. I have a 2004, 3.9 with 150k. After a short drive (engine at operating temp) I have visible blue burnt oil smoke rising from the engine compartment, driver's side. After a closer look, looking under the car, I see oil on the exhaust downpipe.
I replaced the valve cover gaskets, and I know the leak is not from there.

What can cause a leak that ends up on the exhaust downpipe? Is there a common leak site on these 3.9 engines that's consistent with my description?
I appreciate all your help!
-paul