My 2000 LS 3.0L is ever so famous for the V/C leaking so after the 4th time replacing the gaskets we went deeper into her to see if something would "jump" out.... Well not quite what I was looking for but after taking the fuel lines off and looking at the head there's some kind of black STICKY grime on her... WTF?? Carbon build up I understand, but I've never seen this sticky stuff before.. Its about 6cm thick in spots around where the injectors spray into the head. Anyone else seen this before?