Are the water pipes connected to the throttle body regulated by a thermostat? If not, does this heating contribute to higher intake temperatures during the summer?

 

No (not seperately to the main cooland thermostat anyways) and yes (it's fairly straightforward to bypass the throttle body coolant lines, just wrap one of the lines straight back into the other side at the block connection point.

 

The throttle body is heated, as is the ISC, to prevent carb icing.

By heating the throttle body, rather than the air, the effect on performance is negligeable.

Carb icing can take place in ambient air temps as high as 21degC, but is very unlikely on a turbo car as the intake air is normally much higher than this. A longer spell on light throttle cruise would be the most ideal conditions for it to occur.

Heating the body doesn't stop carb icing, but the ice can't stick and choke the air supply. As it can't stick, the ice goes through the engine and this is completely harmless.

 

What benefits would you see from an increased throttle body(size) - say one from a large USA motor like the one David Wallis is using??

Chris