They are pop rivets. If you push from underneath it will stick out enough that you can pull the entire thing out (center piece, and surrounding plastic).. When you want to put it back together you just push the center piece back down and it clicks into place. It's the same concept as a drywall anchor that you can reuse. Hold the surrounding plastic piece down and push up from underneath. I can do it without tools but it hurts the fingers a bit.

I don't recommend pushing it through as it could go all the way through and fall below your inter-cooler. I've dropped a screw down there once and it was a bitch to get out.

This is similar to what the piece looks like when it's out.