Split the pork tenderloins down the centre, cutting just deep enough so they open flat. Season to taste with salt and pepper.
Combine chopped peppers and 1 tablespoon balsamic vinegar. Add bread crumbs, 1/4 tsp each salt and pepper. Toss well. Spoon the stuffing down the centre of each tenderloin. Close up the tenderloins and tie with kitchen string in several places.
Place tenderloins on rack in roasting pan and cook at 350º for 40 to 50 minutes or until meat thermometer registers 160º. Meanwhile, in a small sauce pan, heat oil over low heat. Add shallots or onions and cook about 2 minutes or until tender. Stir in gravy mix and water and prepare as directed on the package. Stir in remaining 1 tbsp balsamic vinegar.
Transfer the pork to a platter, snip the strings and discard. Cut meat into 1” thick slices. Serve with gravy, roasted red potatoes, sliced zucchini and carrots.
*Bake whole peppers in 400º oven for 20 to 30 minutes turning once or twice until blackened and blistered. Scrape skin from peppers, discard seeds, chop and drain peppers.