Smoking exhaust--help diagnosing!

[okto]

After a hard drive today, I noticed steam/smoke wisping out from under Ilse's hood. She blew a heater hose recently, so I figured it was a coolant leak. Howver, when I popped the hood, I found that it was smoke coming from the rearmost part of the exhaust manifold, right where it joins the downpipe. I just started running B100 and my injector return lines are kind of oozy, but this smelled like oil. Also, the exhaust manifold is discolored like it's soaked in oil, just right at the back. I had noticed this before, but written it off to the remains of some long-ago leak, as pretty much every part of the engine was a greasy mess when I bought it.

Any ideas, fellow dieselers? I don't see anywhere oil could be dripping onto the manifold. The back of the engine looks pretty wet, the bellhousing seems to be covered, but I haven't noticed a puddle on the pavement where I park, so I assumed that also was expected quarter-million-mile engine mess.