Cleaning up the garage after installing intake manifold gaskets on my 2000 Tahoe 5.3L, I found a second insulation piece under the truck. I installed the one under the front when reassembling, I seem to have omitted the one that goes in the rear.

Is this important at all?

I have done many engine repairs in my life, this was my first Vortec... Didn't know these foam insulation blocks even existed.