I don't think I even need to put the JB on them. Mainly doing it to ensure they stay where they are and don't allow miniscule vacuum leaks.
I have some of this picture sealant.
Says it's good for gasoline and up to 250*C. Which is like 482*F. But I'm not sure how hot exhaust is at that point?
I'm going to put an egr block off plate. But that blocks 1 side. Not the other.
It actually looks like it won't block exhaust from going through the passage. Just from getting to them plugs. Which may be enough.