Hi. Just replacing the thermostat housing and had to take off the throttle body etc.

I looked into the hole which I assume is the intake manifold and it is fouled with gas/oil residue.

Not knowing - is this normal or should it be squeaky clean?

 

Not sure but does not your PCV valve connect to your intake manifold, so that could explain any oily residue. Will check on mine...

Of course have one, but not a 4.4

 

It will never be clean without an oil separator in the PCV line. Does seem like the 4.4 loves to suck in oil more than most vehicles I have had. My understanding is that when the PCV valve fails it causes the engine to not run well. But maybe before they full out die they also allow more "blow by" of oil. So replacement may cut it back. The design of the valve itself seems like its suppose to nearly eliminate the oil issue though, just does not work well.

 

Wait until you take an intake off and stand it on end. I usually see around 1/2 liter of oil dump out. It just collects in the bottom and sits there.