Add ½ of the butter (2 Tbsp) and the Italian sausage links to the bottom on pot.
"Saute" sausage until all sides are browned then remove from pot.
Slice sausage into ½" slices and add back to pot.
Add remaining butter and scrape the bottom to remove any bits of brown, then add sliced bell peppers, onions and garlic to IP.
"Saute" until bell peppers are soft, about 3-4 minutes.
Add, oregano, basil, pepper and stir.
Next, add the remaining ingredients and stir, except for cheese.
Close and lock lid, turn vent to "sealing" and press "Manual" "High Pressure" and set the time for 6 minutes (takes about 20 minutes to reach to full pressure).
When finished, natural release for 5 minutes then quick release.
Open lid once the float valve drops, add shredded cheese, stir and serve.
Serve with side salad and garlic bread.