Auto Parts: tiny bit of coolant in oil I think, head gasket, filler neck

Question
I just bought a 99 mustang GT from someone and I noticed that inside the oil filler neck and cap there's the ominous white goo.  also in the PCV line, same sludge.  I know that means i have a leak somewhere but what is strange to me is that the dipstick is clean and I drained the oil and its clean too, and the oil filter was clean of goo as well.  I've even checked the stick when running and its not milky or "fudgey" or anything. the view down the filler neck shows squeaky clean cams etc.  I cleaned the inside of the filler neck and ran the car about 200 miles and it there's some new goo back but not much.  
Does this sound like a crack somewhere or a head gasket? it seems like too small of a leak for that. should I just keep it clean and make sure doesnt get worse?
any help would be MUCH appreciated!
thanks!

Answer
It's fairly normal if the car is not driven on long distances on a consistent basis.  The engine needs to get good and heat-soaked in order to burn off any excess moisture.  At the filler cap is where you'll see the most evidence of moisture.  If the engine looks clean and there's nothing suspicious in the oil I wouldn't worry about it.