This is discussed at least twice a week.
Concensus?
Not required?
Yes, Required
Exhaust manifold heat?
Works fine
Hot water heat?
Works fine
Some intakes allow "flow" of heated water (Offenhauser) and some do not (Fenton). If no true flow, you simple get contact heat transfer (which is good enough).
I have used both methods. I now use heat tubes from the Fenton headers to a plate on the bottom of the intake manifold.
