Heat butter in large heavy saucepan. Add the garlic and sausage, stirring and breaking up, until sausage is no longer pink. Remove the sausage and set aside. In remaining butter and sausage juices, brown the pork loin on all sides over medium high heat. Drain off excess fat.
Add about 1/2 the onions, all the tomatoes, chicken broth, and reserved sausage to the saucepan with the loin. Add salt and pepper to taste. Cover and simmer for about 2 1/2 hours on low.
In a skillet, over medium heat, sauté remaining onion and peppers in butter, until tender-crisp. Season with favourite vegetable mix or just salt and pepper.
Remove the pork loin and slice, setting aside while you make the gravy.
Separate the sausage, onions and tomatoes from the remaining broth using a slotted spoon and set aside. Combine the flour and warm water until smooth, Stir the flour mixture into the pork juices in saucepan over medium heat, a little a time, until thickened. Pour gravy over the pork loin on a warmed serving tray and serve with the sautéd onions and peppers.