Go back to Spiral Mountain and use the Flight Pad to fly up to a waterfall with a hole in it. Jump all the way through the rushing current to find the Game Pak. Go to where the Game Pak is located, then do a backflip near the waterfall inside there. You should hang from a crack -- slide to your right, go under the waterfall, and press A. If done correctly, you can get up and just walk through that tunnel to find it.