Preheat oven to 325°F.
Heat the oil in a large Dutch oven or other large oven-safe pot over medium high heat. Trim the pork of excess fat and cut it into 4 or 5 equal pieces. Season the pieces generously on all sides with salt and pepper. Add the pork to the pot and brown the meat on all sides, about 8-10 minutes. Remove the pork from the pot and set aside.
Lower the heat to medium and add the onions. Sweat the onions until softened, 6-8 minutes. Add the garlic, bay leaf, chipotle peppers, adobo sauce, cumin, oregano, allspice, diced tomatoes and chicken stock (or water) and stir to combine. Add the browned pork back to the pot. Bring to a simmer, then cover the pot and place in the oven. Cook 2-2 ½ hours until meat is fork tender.
While the pork is cooking, make the corn jalapeno salsa. Mix all of the ingredients for the salsa together in a medium bowl. Season with salt to taste. Refrigerate until ready to use.
When the pork is done, remove from the pot from the oven. Remove the pork pieces from the pot and place them on a cutting board or plate. Using two forks, pull the meat apart into pieces. In the meantime, bring the sauce in the pot to a simmer on the stove. Add the vinegar and simmer another few minutes. Taste the sauce and season with salt and pepper to taste. Put the shredded pork back into the sauce and stir to coat all of the meat with the sauce. Add more chicken stock or water as needed. The meat should be juicy and coated with sauce but it should not be soupy.
To assemble the tacos, place some of the braised pork on a tortilla. Top with some corn jalapeno salsa. Drizzle with sour cream and shredded lettuce if desired. Serve with lime wedges on the side. Enjoy with a cold Mexican beer or beverage of your choice!