Combine water, macaroni pasta, mustard powder, salt and chilli sauce in an electric pressure cooker (such as Instant Pot®). Close and lock the lid. Set timer for 4 minutes. Set to high pressure according to manufacturer's instructions, 10 to 15 minutes.
Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove lid. Switch to 'Low Saute' function by pressing 'Saute' once and 'Adjust' twice. Stir macaroni to separate any clumps.
Stir evaporated milk, milk and butter into the pot. Add grated cheeses gradually, stirring constantly until melted. Stir in ham and peas. Season with salt and pepper.