breaking the porcelain shouldnt be a prob at all on the way out....hell your just gonna throw them away anyway...

 

Chrysler put those there for a reason. It's to preserve the plastic on the spark plug wires, as there is some pretty intense heat down there above the exhaust manifold, even worse because of convection.

 

well you think if they really wanted to keep the heat shield idea they would have gone with a half shield. more room to access the plug but it still guards from the heat. i don't know, its a toss up on this issue. i was gonna remove mine whenever i do my plugs. has anyone had problems after removing the shields?

 

I believe freeze off has very similar chemicals when compared to Knock'er Loose with the added freezing chemical. It won't damage anything with the freezing factor.
The porcelain breaking isn't a problem, the threads getting hosed up is. I've broken a couple, it just makes the plug unusable.
My headers sit around 400º at idle just to give you an idea. I would think that the only concern would be the plug boot melting and allowing moisture to seep in there, or exposing the inner part of the wire and getting cross fire.