Add the cooking oil to the Instant Pot and brown the pork on all sides right in the Instant Pot, about 6 minutes per side.
Add the chicken broth, water, sake and dashi powder. Use the pressure cooker setting (high) to cook for 45 minutes. Use the quick release to release the pressure. Let the pressure release naturally for 15 minutes, then use quick release to release any remaining pressure.
Remove the pork from the broth and break into pieces on a lined baking sheet.
Sprinkle the brown sugar and dark soy sauce on the pork pieces, mix well and broil until pork is caramelized (5-10 minutes), being careful not to let the sugar burn.
Add the fish sauce, soy sauce, black pepper, chili garlic paste, and rice wine vinegar to the broth. Set the Instant Pot to the saute setting and bring to a simmer for 5 minutes.
While the broth simmers, cook the dried ramen noodles in boiling water for 3 minutes. Drain.
Place the noodles in bowl and cover with broth.
Add braised pork belly, caramelized pork pieces, green onions, 1-2 ramen eggs (halved) and garnishes, if desired.