Or if there is metal underneath, it might be insulated with something like aerogel, between the alloy and the carbon composite. Hence reducing the thermal losses in the exhaust and increasing thermal efficiency.

I doubt there’s metal underneath, as they’d probably have different expansion ratios under heating. Besides wouldn’t make a lot of sense using both. (weight) Obviously wouldn’t be normal carbon composite (resins) due to heat. So possibly a form of Carbon reinforced Carbon?

Because a supercharger is thermally ineffeicient! It requires energy from the crank (and hence from the energy being directly produced by the engine) to power it. Where as a turbo uses otherwise wasted enegy to power it (hot exhaust gases) so is more thermally and hence fuel efficient. So by using the MGU-H, they can…