PB blaster and work the plug back and forth. the tube can be pulled out (it's a friction fit) with some penetrating oil and a pair of needle nose vice grips. they're heat shields to keep ex. manifold heat off the boots.

1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)