Add pasta, seasonings, butter, seafood stock, stock cubes and water to equal 4 cups of liquid to the Instant Pot. Cook on high pressure for 4 minutes, and natural release for 4 minutes, then quick release. Check pasta for doneness and cook for 1 to 2 minutes longer if not cooked through. Add remaining ingredients and mix. Cook on high slow cook for 20 minutes or until cheese is melted. Adjust seasoning.