Set the Instant Pot to saute mode and add the olive oil.
Add the Italian sausage (casings removed) to the Instant Pot and break the sausage up into small pieces as it browns.
Add the diced onions and chopped bell peppers, along with the Italian seasoning, salt and pepper.
Stir everything together and let the veggies soften while the sausage browns.
Remove the sausage and veggies to a plate and add a splash of chicken stock to deglaze the pan. Scrape up all the caramelized bits - this will help you avoid the dreaded burn notice while pressure cooking.
Add about 2 cups of the stock to the Instant Pot and cancel the saute mode.
Add about half the noodles gently into the stock, along with half the diced tomatoes and then half the meat/veggie mixture.
Add the rest of the stock, and then gently add the rest of the noodles, the rest of the tomatoes, and then the rest of the meat/veggie mixture.
Don't stir. Just make sure the noodles are completely submerged in the liquid.
Add the lid to the Instant Pot and set the valve to sealing. Set the Instant Pot to cook on High Pressure for 7 minutes (the Instant Pot will take about 8 minutes to come to full pressure before the 7-minute cooking time begins).
Once the Instant Pot has finished the 7-minute cooking time, release the pressure manually by moving the valve to venting. It's best to do this under a hood fan if you have one in your kitchen, and by using a long-handled kitchen tool to move the valve (to prevent burning yourself).
Once the pressure has released completely, remove the lid immediately.
Stir the noodles and the sauce, helping the noodles separate if any are clumped together. As you toss a meaty sauce will form around the pasta. You can add the parmesan cheese at this stage too, or simply serve the pasta with parmesan cheese on top.
Serve the pasta immediately in its sauce with a sprinkling of parmesan cheese and some chopped fresh herbs (optional).