At the start of the course, take the right path this time, navigating past the fire jets and Scuttle Bugs. In the Work Elevator area, head to the ground and locate the one wooden door on the side, which leads to a small room with a small hole in the ground. Dropping down this hole will bring you to the Hazy Maze, where toxic gas will be present throughout. Anytime you’re standing in the gas (mostly when your head is underneath it), you will slowly lose health, similar to being underwater. As usual, collecting coins will refill your health, but Mario having the Metal Cap equipped will also protect him from losing health.
Once you’re in the Hazy Maze, move straight ahead and get the Metal Cap on, then follow that path around the corner. You should see a safe ledge ahead with a Blue Coin Block, so go there to take a breather. There will be a little cave-like area near you, with another Metal Cap box, as well as four Swoops. Refresh your Metal Cap and go into that area, turn the corner to your left and look for the hole in the wall. Jump to that hole and go through the door, leading to an elevator that brings you to the star.