Have you checked to make sure the oil cap is sealing properly. Sometimes, one of the metal tabs does not grab underneath and it will leak out if both tabs are not correctly positioned (ask me how I know).

Otherwise, you may not have positioned the gasket correctly around the cam area.

__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles