I heat wrapped mine and fitted and stainless heat shield, the insulation from the wrap is probably enough to be honest.
Also helps with keeping exhaust gas hot which inturn aids it's flow . . Apparently.
You can also buy sticky back heat proofing you can use on the bulkhead but must not be in contact with the hot manifold. I didn't do this myself but I could feal the extra heat from the sports cat through the floor and considered adding some under the carpet. But have since sold the ST150 so can't say how effective that would be.