Ben,
A guess at your first question:
I suspect tightening emissions laws. that the crankcase now "breaths" back into the inlet side of the engine rather than to the atmosphere.
My old MGA is vented to the atmosphere but the MGB, with basically the same engine breaths back into the engine. Most modern engines now are so sensitive to this that if you take the oil filler cap off the rocker cover the engine will stall.
In answer to your second question:
Basically you are correct the lower the intake temperature the better, but there are caveats to this in engine design.
I suspect the heating element turns on when the engine and or and air temperatures are very low. Although petrol is sprayed from the injectors if the temperature is low it will tend to pool and condense on the walls of the intake manifold.
In addition it is possible that the venturi effects can cause water vapour to fall out of the air and form ice.
THis will happen in some types of carburettors, usually fixed jet types more than SU types.
Most cars have some system for warming the air going into carbs, wether an automatic flap arrangement or a lever you twiddle for "winter" and "summer". All piston engine aircraft have either carb or manifold heaters to stop ice forming.
With no traditional choke on the injection system this is possibly the solution MB can up with, others, notably BMW with the mechanical injection system used an "overfueling" system with a water temperature adjusting valve in combination with a very crude cold start electric injector.
Once your engine is warm enough I suspect the heater will turn off
I am sure somebody will correct me if I have got this all wrong!
Malc
