Is there any product that can help reduce engine noise into the cabin?

[swidd]

I've eliminated most sources of sound into the cabin, but the engine remains a loud source, especially at higher RPM.

I was wondering if there's any product, generic or yaris specific, for covering/creating a more solid sound barrier under the hood? I've seen under the hood of Audis and BMWs; they have large strong shields over the top of the firewall and engine, in addition to the firewall itself. Have anyone tried making something similar for the Yaris?