I agree with Paul that if the heat is contained around the manifold, it will also be held in the head, around the exhaust ports in particular.
The 2L Duratec has the cat under the wing, and the wing gets very hot above the cat. That's why I fitted an insulting jacket around my cat to keep the wing cooler. It may be possible to fit a second heat shield over the top of your cat (with space between) to prevent heat radiating upwards. Having the inlet pipe directly over the top will increase air temp significantly, and the narrow bore looks quite restrictive.
