In addition to what Bill said about the oil return line on the turbo, the oil filler cap gasket hardens and oil pools on the top of the engine and eventually works its way down the back of the engine.

You can verify this by taking the plastic cover off the top of the engine ... if there's oil sitting in areas on top of the head, that's likely the culprit. A new gasket is only a few bucks at the dealer. Many change them every 10K or so just to keep them fresh.

I had your exact symptoms ... did both the filler cap gasket and the turbo oil return line and now it's dry as a bone.

If your car is a non-turbo, clean the flame trap first before looking for other leaks.

Good Luck,

Keith