VT 304 Metal Insulated Spark Plug Leads Required?

[Nut Kracker]

Hey all,
Is it still necessary to have the metal insulator type spark plug leads when extractors are fitted.?
I know they were required with the old manifold because of the heat, but are they now with extractors.?

 

[showbags]

They're only heat shields to stop you leads from melting. I'd say lead life would be decreased if you don't use them, from that pic, pipes still look pretty close.

 

[Nut Kracker]

Thanks for that.
The thing is, i've just notice now, that 2 of the leads haven't got the heat shield on them and they look fine.
The engine was rebuilt about 12 months ago, so they must have been off at least since then.