What is this thick, black panel on my firewall?

[pgt892]

I was cleaning up my engine bay today and I noticed this black panel behind the engine. It was only held onto the firewall with one 10mm bolt so I took it out. It was pretty solid and heavy. I asked my dad and he said maybe it was for engine vibration or heat. I looked in the FSM and couldn't see anything about it. So tell me, do you know what this black panel is/does? Thanks.

[slow s13]

Im almost positive its for noise vibration coming from the ac compressor. but its right on the firewall where the ac line runs up against the car for the first time correct? chuck it its only slowing you down hhehehe.

[pgt892]

Yes, it was behind the AC compressor line. I actually was taking that out yesterday and that is when I noticed it. If it's not needed for anything like heat or engine vibration then it should be ok to take out?