As I said, any grease-based lube around a heat riser isn't a good idea. I have monitored exhaust gas temps at cylinder head ports in the 2K degree F. range on a hard dyno pull. I don't know of any lube that will stay put when a cast iron manifold approaches a dull red color, but dry graphite has a better chance of it than any liquid or paste.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!