Combine jalapenos, garlic, salt and vinegar in a food processor. Pulse until jalapenos and garlic are finely diced. Transfer to a large bowl and stir in olive oil.
Use a knife to put shallow cuts all over the pork shoulder. Place the pork in the marinade and turn to coat completely. Cover and refrigerate for 6 hours or overnight.
Preheat oven to 350 degrees.
Place the pork in a baking dish. Pour the excess marinade over the top. Bake uncovered in preheated oven for 3 hours or until a thermometer reaches 160 degrees. Remove from oven and allow to rest 10 minutes before slicing or shredding.