Scrape off excess marinade from pork; season evenly with salt. ln large, heavy, ovenproof sauté pan, heat oil over medium-high heat. Brown pork on all sides. (Be careful not to burn pork; marinade contains sugar that will burn quickly.) Roast in 375°F oven 5 minutes. Brush pork generously with barbecue sauce; roast 10-15 minutes more or until a thermometer registers 155-176°F (pork should be slightly pink on the inside). Let rest 5 minutes before slicing. Serve with guacamole on the side.
Note: If you can't find guarapo, make diluted simple syrup by combining 1/3 cup sugar with 1 cup water in a small saucepan. Bring just to a boil, stirring until the sugar dissolves. Remove from heat and cool before using.
To make Mango Barbecue Sauce: In large saucepan over medium heat, combine 1/4 cup diced onions, 2 large mangoes, peeled, seeded and chopped, 1 canned chipotle in adobo sauce, 1 tablespoon Worcestershire sauce, 1 tablespoon ketchup, 1/4 cup cider vinegar, 1 tablespoon hot sauce, 2 tablespoons olive oil, 1/4 cup light brown sugar, pinch salt, 1 1/2 teaspoons Kikkoman Soy Sauce and half a roasted red pepper. Bring to a boil, reduce heat to medium-low and simmer, covered, until mangoes are very tender, about 15 minutes. Allow to cool slightly; transfer to a blender. Add 1 tablespoon Worcestershire sauce, 1 1/2 teaspoons honey, 1 teaspoon lime juice and 1 tablespoon of water; purée until smooth. Refrigerate. Can be made up to 5 days ahead. (Yield: 2 cups)
Recipe by Chef Guillermo Pernot, Cuba Libre Restaurant & Rum Bar (Philadelphia & Atlantic City)