Cook chopped bacon in the Instant Pot on Medium Saute until brown, stirring constantly. Remove the bacon along with all but 1 tablespoon of the grease. Set bacon aside, and refrigerate extra bacon grease for use another time. (Alternately, you can cook the bacon in the oven at 350 degrees while the macaroni is cooking in the Instant Pot, and chop it after cooking.)
Add the macaroni and water to the pot. Cook on manual for 4 minutes. Do a careful quick release of the pressure.
Add the butter to the warm noodles in the pot, and stir until melted.
In a medium bowl, stir together the eggs, milk, mustard powder, paprika, and cayenne pepper. Pour the mixture into the Instant Pot and stir to combine. (The hot noodles will cook the egg mixture.) Stir in the grated cheese until melted. Add salt and pepper to taste.
To serve, top with chopped bacon, scallions, and steamed broccoli bits.