I got great results in refinishing the under hood insulation pad by:
- carefully clamping it to a 4' x 4' piece of plywood
- soaking it in engine degreaser and rinsing it out (repeat this step as many times as needed to get it reasonably clean)
- letting it dry throughly
- spray painting it flat black (as many coats as required, I needed 4 coats)
My pad was pretty good to begin with but it still had that splotchy gray / black color to it. They might have come from the factory colored that way.
Now it's a nice solid uniform black.
My hood is completely painted on the underside from when I painted the body but I wanted to use the insulator to protect the hood Spyder decal from the engine heat.
I've seen and heard that the engine heat can / will damage the decal.
Paul