so you want to lower the temperature of the exhaust manifold? you don't want to do that, a hotter exhaust manifold flows faster then a colder one and creates a better scavenging effect. just use thermal wrap on the manifold, buy better (grade A) bolts, take them to a shop and get them ceramic coated if you don't feel that's enough. use insulation on the intake tube, a spray bar on the intercooler and a thermal gasket on the intake manifold and you will lower the intake charge temperature.

and if you REALLY want to lower the intake temp then run water/methonal injection or a small amount of nitrous.

custom240sx is right in that everything will heat soak, especially the intake and the intercooler.

all i did to my car is replace the thermostat with a restrictor and straight wired my fan, i always turn it on at a red light. even on these insanely hot days my engine temp never goes past 1/4.