[shorod]

Like RahX said above, I would agree that some film in the intake is not uncommon. Mostly what I've seen I would attribute to vapors from the PCV system doing its job, and I suspect if the vehicle sees a lot of in-town driving and not so much highway driving it may never burn itself clean. What I've experienced I would agree has a petroleum smell, I'm not sure sure I'd pin it as a fuel smell, although there is a hint of fuel odor to it.

Keep in mind that if it's truly just fuel vapors it would have evaporated in the time the intake manifold was removed from the engine and sitting on the garage floor/work bench. I would suspect the majority of what you are seeing/smelling is oil from the PCV system.

-Rod