The spacer itself isn't made of Cu. OTOH, The polarized throttle body heater is made of copper and its made to specifically heat only the throttle body while leaving everything else thermally isolated.

In the stock configuration, hot engine coolant is flowed out of the engine and into the whole upper and lower plenum assembly to make sure the throttle body is heated. This is for safety reasons. It is to prevent ice formation on the inside of the throttle body on really cold days.



The tube shown in the picture above is where the hot coolant is re-routed from the plenum to the polarized copper throttle body heater.

The bare side of the copper bolts up to the throttle body where it transfers heat into only the throttlebody to prevent ice formation during cold weather.

The insulated side of the copper bolts up to the plenum where there is no heat transfer.

So, instead of heating the entire upper and lower plenum like stock, the copper transfers heat only into the throttle body. This will allow for safe driving in cold weather and at the same time it will let the plenum assembly to run a lot cooler.

Tony