During inspection today of my 98' Duratec (92,000 miles) pulled air filter and noticed a small trace of oil inside the flex (accordian) tube right where the rear vent hose plugs in. Is this normal? I started to wonder about oil entering the throttle body so I pulled flex tube off and looked inside the brass flapper and on the rear side of the flapper there was a black oily film. I've seen black soot on the inside of a throttle plate before but it wasn't oily (wet). I'm wondering if this is normal or if this is a sign of an interior engine problem. Anyone have any ideas? Should the throttle body be "pulling" oil from the vent tube?