Talk about the proverbial can of worms...
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That is what every vortec I have ever done looks when I have taken the intake apart, from the 4.3 to the 7.4, it's the EGR that contributes most of the crap you see inside the manifold! never have seen one clean but we don't eliminate the EGR or any like that, good carb clean spray, a stiff brush and lots of elbow grease will eliminate all the build up!
Make sure You use fel-pro MS98000T gasket set when you put the lower intake back on, DO NOT use the original type gaskets, they are crap and you will be redoing the whole mess in no time!!
The hose you are looking for is the vacuum supply to the heater control valve and I never have found an original replacement so I use vacuum hose to fix the break just like rayra explained!