Trim fat from the pork. Rub pork with the olive oil. In a small bowl combine the chili powder, ancho chile pepper, cumin, oregano, 1 teaspoon black pepper, and 1 teaspoon salt. Rub mixture all over pork until well coated. Let stand at room temperature for 30 minutes or cover and refrigerate up to 2 hours.
For a charcoal grill, arrange medium-hot coals around a drip pan. Place pork on greased grill rack over drip pan. Cover; grill 30 to 35 minutes or until slightly pink in the center (155 degrees F). (For a gas grill, preheat grill. Reduce heat to medium. Adjust for indirect cooking. Place pork on greased rack on unheated side of grill. Cover; grill as above.) Remove pork from grill; tent with foil and let rest 15 minutes.
To serve, cut pork into very thin slices and place on a platter. Top with Pineapple and Papaya Salsa, pumpkin seeds, and cilantro sprigs. Makes 6 servings.
In a large bowl gently toss together all ingredients. Season to taste with salt.