exhaust manifold heat shield (noise)

[rayfloyd170]

Last 6 months ago, I heard some minimal rattling sound due to the exhaust manifold heat shield specially during low rev and during acceleration.

I removed 3 bolts holding the heatshield and could not find any suspect other than some kind of circular metal washer "sponge" but it is fixed and could not be removed. i was thinking this could come a little loose and generating the noise.

i have managed to solve the issue by putting a small amount of white grease
on the metal "sponge" washer and this temporarily solves the problem for some time. Now, intermittently this noise is coming back and again i put some grease and this puts the noise away.

Other than completely removing the exhaust heatshield, what can you suggest to permanently eliminate this minimal rattling noise?

What kind of grease is best suited for this?

Thanks in adv.