I need to finish a spark plug change on the Magnum today. Had to pull the intake plenum to get to them. Needed a few things to finish and didn't have another vehicle to run for parts till later in evening. Anybody familiar with this... Had foam under plastic plenum. It was half goo and half dust. I cleaned it all off, but wondmering how important it is, cause have nothing good to replace it with. Read some other forums- some say its for heat, other say sound.