Pressurized Mash Tun?

Has anyone tried to hook up pressurized air to their cooler mash tun to get all the wort out of it to increase efficiency?

Nope. Interesting concept, though. You shouldn't be having issues with efficiency if you're using the right amount of H2O for the mash and sparge. It also helps to stir the tun every 20 minutes so you make sure the grain on top works as hard as the stuff at the bottom. I was initially taught not to do that ... then someone asked why not?