The heatshields from Autobarn are pretty useless, although the may offer some protection from direct radiant heat from the engine or radiator, they offer no protection from the ambient heat under your bonnet, which is the real issue.
The best option is some sort of divider, to section off the air filter, and a cold air inlet from the front bumper
i dont remember who make its but some company makes a filter which already has its own enclosure and has a pipe after it so you can get proper cold air.