Accord noise: OK to insulate Ex. Man. Shield?

I have a '94 LX Wagon which I love, except for the noise.

My next step in quieting the thing down is to tackle the exhaust
manifold, which I've determined is the source of most of the remaining
engine noise.

I took some under the hood insulation out of some cars in a junkyard
and found that if I temporarily cover that shield over the exhaust
manifold, things get much quieter.

I need to know from you guys what I could use permanently as a sound
insulator on that shield or if it is even advisable.

I'm concerned about heat rejection and the possibility of warping the
manifold (or engine!).

There's WAY too much road and engine noise for a car that originally
cost almost $20,000. I've already insulated the hood and put down
sound insulating foam rubber mats under the carpet.

Both helped, but the car still growls too much under hard acceleration
or when I load it up with the family.

I've had the Buzz Kit installed, which helped.

Thanks for your help!

P.S. After this, I tackle the road noise.

 

The shield is there to protect the paint on the hood. It should be ok as
long as you have something nonflammable on it.

 

Excellent! Thanks. I was wondering what it was for.

Would insulation used for under a car's hood be nonflammable enough?