On Planet Todando, after you enter the facility (way after you reach a continue point), as in the first part of it, after you kill everyone, go to the arch you're supposed to go to proceed, but wait! Two boxes should be on your left. Blow them up, because behind them is an Infiltrator spot. It's freaking hard, but if you succeed, an elevator will drop down on your left. Go on it and it'll take you to a higher platform. Follo that path and you'll find a Nanotech Health Upgrade!